docs: complete 4.0 upgrade guide for merged breaking changes

[DavidBadura]

Why

Several breaking changes from already-merged 4.0 PRs were missing from the upgrade guide. This adds them so the guide reflects the current 4.0.x state.

What

Added to docs/UPGRADE-4.0.md:

• Stream refactor (refactor stream #847): Store\Stream interface removed and replaced by the concrete Message\Stream class; removed store-specific stream implementations (ArrayStream, StreamDoctrineDbalStoreStream, TaggableDoctrineDbalStoreStream, GeneratorStream); Message\Pipe removed in favor of Stream::transform() (with before/after example).
• remove deprecated subscriber util and helper #805: removed deprecated SubscriberHelper and SubscriberUtil trait.
• remove deprecations in subscriptions #756: removed SubscriberAccessor / RealSubscriberAccessor interfaces (use MetadataSubscriberAccessor directly), removed deprecated id()/group()/runMode() accessor methods, removed AggregateIdArgumentResolver.
• use type info in argument resolver #814: ArgumentMetadata::$type is now a Symfony\Component\TypeInfo\Type instead of string + allowsNull.

Updated docs/message.md:

• Reworked the Pipe section into a Stream section using the new Stream::transform() API.

Notes

• Only merged breaking changes are documented. Still-open PRs (Refactor subscription engine #848, Repository store adapter #816, upgrade hydrator 2.0 #777, Use jsonb when using postgresql #671) are intentionally left out until merged.
• docs/testing.md was left untouched: its SubscriberUtilities (namespace PhpUnit\Test) is unrelated to the removed Subscription\Subscriber\SubscriberHelper/SubscriberUtil.

[github-actions]

Hello 👋

here is the most recent benchmark result:

SplitStreamBench
================

+-------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
|                         | time (kde mode)                                     | memory                                     |
+-------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
| subject                 | Tag: <current>     | Tag: base          | time-diff | Tag: <current>  | Tag: base  | memory-diff |
+-------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
| benchLoad10000Events () | 3.553ms (±0.00%)   | 3.484ms (±0.00%)   | +2.01%    | 35.834mb        | 36.286mb   | -1.25%      |
| benchSave10000Events () | 500.519ms (±0.00%) | 512.563ms (±0.00%) | -2.35%    | 35.903mb        | 36.421mb   | -1.42%      |
+-------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+

SimpleSetupStreamStoreBench
===========================

+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
|                                        | time (kde mode)                                     | memory                                     |
+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
| subject                                | Tag: <current>     | Tag: base          | time-diff | Tag: <current>  | Tag: base  | memory-diff |
+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
| benchLoad1Event ()                     | 1.174ms (±0.00%)   | 1.192ms (±0.00%)   | -1.53%    | 35.140mb        | 35.140mb   | 0.00%       |
| benchLoad10000Events ()                | 72.937ms (±0.00%)  | 71.709ms (±0.00%)  | +1.71%    | 35.140mb        | 35.140mb   | 0.00%       |
| benchSave1Event ()                     | 1.449ms (±0.00%)   | 1.454ms (±0.00%)   | -0.36%    | 35.140mb        | 35.140mb   | 0.00%       |
| benchSave10000Events ()                | 284.145ms (±0.00%) | 288.048ms (±0.00%) | -1.36%    | 35.140mb        | 35.140mb   | 0.00%       |
| benchSave10000Aggregates ()            | 9.011s (±0.00%)    | 8.887s (±0.00%)    | +1.39%    | 35.140mb        | 35.140mb   | 0.00%       |
| benchSave10000AggregatesTransaction () | 5.688s (±0.00%)    | 5.691s (±0.00%)    | -0.04%    | 35.140mb        | 35.140mb   | 0.00%       |
+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+

SubscriptionEngineBatchBench
============================

+---------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
|                           | time (kde mode)                                     | memory                                     |
+---------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
| subject                   | Tag: <current>     | Tag: base          | time-diff | Tag: <current>  | Tag: base  | memory-diff |
+---------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
| benchHandle10000Events () | 103.089ms (±0.00%) | 100.480ms (±0.00%) | +2.60%    | 35.720mb        | 35.720mb   | 0.00%       |
+---------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+

SubscriptionEngineBench
=======================

+---------------------------+-----------------+-----------------+-----------+-----------------+------------+-------------+
|                           | time (kde mode)                               | memory                                     |
+---------------------------+-----------------+-----------------+-----------+-----------------+------------+-------------+
| subject                   | Tag: <current>  | Tag: base       | time-diff | Tag: <current>  | Tag: base  | memory-diff |
+---------------------------+-----------------+-----------------+-----------+-----------------+------------+-------------+
| benchHandle10000Events () | 3.499s (±0.00%) | 3.478s (±0.00%) | +0.59%    | 48.293mb        | 48.293mb   | 0.00%       |
+---------------------------+-----------------+-----------------+-----------+-----------------+------------+-------------+

CommandToQueryBench
===================

+----------------+------------------+------------------+-----------+-----------------+------------+-------------+
|                | time (kde mode)                                 | memory                                     |
+----------------+------------------+------------------+-----------+-----------------+------------+-------------+
| subject        | Tag: <current>   | Tag: base        | time-diff | Tag: <current>  | Tag: base  | memory-diff |
+----------------+------------------+------------------+-----------+-----------------+------------+-------------+
| benchCreate () | 2.722ms (±0.00%) | 2.778ms (±0.00%) | -2.03%    | 5.005mb         | 5.005mb    | 0.00%       |
| benchUpdate () | 4.065ms (±0.00%) | 4.146ms (±0.00%) | -1.95%    | 5.014mb         | 5.014mb    | 0.00%       |
| benchBoth ()   | 7.184ms (±0.00%) | 7.357ms (±0.00%) | -2.36%    | 5.752mb         | 5.752mb    | 0.00%       |
+----------------+------------------+------------------+-----------+-----------------+------------+-------------+

PersonalDataBench
=================

+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
|                                        | time (kde mode)                                     | memory                                     |
+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
| subject                                | Tag: <current>     | Tag: base          | time-diff | Tag: <current>  | Tag: base  | memory-diff |
+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
| benchLoad1Event ()                     | 1.194ms (±0.00%)   | 1.212ms (±0.00%)   | -1.46%    | 35.804mb        | 35.804mb   | 0.00%       |
| benchLoad10000Events ()                | 109.736ms (±0.00%) | 109.140ms (±0.00%) | +0.55%    | 35.804mb        | 35.804mb   | 0.00%       |
| benchSave1Event ()                     | 1.892ms (±0.00%)   | 1.811ms (±0.00%)   | +4.44%    | 35.804mb        | 35.804mb   | 0.00%       |
| benchSave10000Events ()                | 315.239ms (±0.00%) | 311.908ms (±0.00%) | +1.07%    | 35.806mb        | 35.806mb   | 0.00%       |
| benchSave10000Aggregates ()            | 13.691s (±0.00%)   | 13.836s (±0.00%)   | -1.05%    | 35.804mb        | 35.804mb   | 0.00%       |
| benchSave10000AggregatesTransaction () | 10.357s (±0.00%)   | 10.353s (±0.00%)   | +0.05%    | 36.044mb        | 36.044mb   | 0.00%       |
+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+

SnapshotsBench
==============

+----------------------------------------+-------------------+-------------------+-----------+-----------------+------------+-------------+
|                                        | time (kde mode)                                   | memory                                     |
+----------------------------------------+-------------------+-------------------+-----------+-----------------+------------+-------------+
| subject                                | Tag: <current>    | Tag: base         | time-diff | Tag: <current>  | Tag: base  | memory-diff |
+----------------------------------------+-------------------+-------------------+-----------+-----------------+------------+-------------+
| benchLoad10000EventsMissingSnapshot () | 71.753ms (±0.00%) | 72.542ms (±0.00%) | -1.09%    | 35.210mb        | 35.210mb   | 0.00%       |
| benchLoad10000Events ()                | 1.372ms (±0.00%)  | 1.371ms (±0.00%)  | +0.12%    | 35.210mb        | 35.210mb   | 0.00%       |
+----------------------------------------+-------------------+-------------------+-----------+-----------------+------------+-------------+

SimpleSetupTaggableStoreBench
=============================

+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
|                                        | time (kde mode)                                     | memory                                     |
+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
| subject                                | Tag: <current>     | Tag: base          | time-diff | Tag: <current>  | Tag: base  | memory-diff |
+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+
| benchLoad1Event ()                     | 1.127ms (±0.00%)   | 1.127ms (±0.00%)   | -0.01%    | 36.306mb        | 36.306mb   | 0.00%       |
| benchLoad10000Events ()                | 75.147ms (±0.00%)  | 75.460ms (±0.00%)  | -0.42%    | 36.306mb        | 36.306mb   | 0.00%       |
| benchSave1Event ()                     | 1.443ms (±0.00%)   | 1.390ms (±0.00%)   | +3.84%    | 36.306mb        | 36.306mb   | 0.00%       |
| benchSave10000Events ()                | 304.212ms (±0.00%) | 304.021ms (±0.00%) | +0.06%    | 36.306mb        | 36.306mb   | 0.00%       |
| benchSave10000Aggregates ()            | 8.979s (±0.00%)    | 9.043s (±0.00%)    | -0.70%    | 36.306mb        | 36.306mb   | 0.00%       |
| benchSave10000AggregatesTransaction () | 5.746s (±0.00%)    | 5.698s (±0.00%)    | +0.84%    | 36.306mb        | 36.306mb   | 0.00%       |
| benchAppend1Event ()                   | 1.526ms (±0.00%)   | 1.521ms (±0.00%)   | +0.34%    | 36.306mb        | 36.306mb   | 0.00%       |
| benchAppend100Events ()                | 7.569ms (±0.00%)   | 7.524ms (±0.00%)   | +0.60%    | 36.306mb        | 36.306mb   | 0.00%       |
+----------------------------------------+--------------------+--------------------+-----------+-----------------+------------+-------------+

This comment gets update everytime a new commit comes in!