Java SDK: Register tasks as first-class TaskDef objects - #71057

Stub tasks silently ignored TaskFlow call arguments, so a Dag author
could not hand literals or upstream XCom results to a lang-SDK runtime.
The decorator now binds the call to the stub's signature at parse time
and captures an ordered arg spec (literal values and direct upstream
XCom references, with pydantic-derived JSON value schemas) that
serializes with the Dag, while rejecting what cannot cross the language
boundary: custom XCom keys, aggregated mapped outputs, non-JSON
literals, and stubs with arguments inside mapped task groups. Mapped
(.expand()) stubs capture no spec and keep the legacy behavior until a
follow-up delivers per-map-index bindings.

TIRunContext gains an arg_bindings field so a lang-SDK runtime receives
the stub task's TaskFlow arg spec at startup. ti_run derives it from the
serialized Dag only for stub operators, so regular tasks never pay for
the lookup, and only for clients on the new API version -- gated on the
Cadwyn VersionChangeWithSideEffects.is_applied check rather than a date
comparison -- so stub Dags that predate arg bindings keep running
against older clients, for which the version migration strips the field.

StartupDetails in the supervisor wire schema carries the new
arg_bindings so foreign runtimes receive the spec at task startup, with
a version migration that strips it for runtimes pinned to the previous
schema. The Go and TS SDKs regenerate against the new schema version;
the Go arg-binding runtime itself lands in a stacked follow-up PR.

An XComArg buried in a list or dict literal fell through to the JSON
check, whose "pass it in its JSON form instead" advice is impossible to
follow for a task output. Detect nested references up front and point
the author at the working alternative: pass the upstream output as its
own argument.

When a PR cuts a new provider version while the previous version is
still being voted on, only the rcN tags exist on the apache remote -
the final tag is pushed after the vote passes. The changes-table walk
in _get_all_changes_for_package assumed every past version has a final
tag and crashed with git exit 128 in that window, breaking CI for any
PR that bumps a provider version during a release wave.

`dag.addTask("extract", Extract.class)` stored tasks as a plain
`Map<String, Class<out Task>>`, which leaves nowhere to hang anything
else a task needs: dependency edges, task-level configuration, and
argument wiring all have to attach to a per-task object, and a map of
classes cannot carry them. Introducing that object now keeps those
follow-ups additive instead of forcing another break of the registration
API later.

The annotation surface keeps `Builder.Dag` / `Builder.Task`, and the
interface users implement keeps the `Task` name, so the definition
objects are `DagDef` and `TaskDef` -- a pairing that stays unambiguous
next to `Task` at a use site. The SDK is pre-1.0, so the old
string-keyed overload is removed outright rather than deprecated.