[python] Add manifest sidecar codec and block-pruned reads

[leaves12138]

Purpose

Extract the Python sidecar core and read integration from #9743, on top of the merged Java v1 format and read support (#9845, #9886, #9889, #9897).

Changes

• Add the standalone v1 sidecar codec, complete block directory, exact row-ID intervals, partition dictionary and bucket coverage, using the shared Java golden file.
• Prune manifest blocks before decoding entries in the Python scan path. Preserve normal entry predicates, column groups and ADD/DELETE reconciliation.
• Read only explicitly referenced sidecars, fall back to normal manifest reads for missing/unusable sidecars, and propagate cancellation/interruption.
• Skip sidecar I/O when disabled, without relevant filters, and in explain/statistics mode.
• Classify sidecars as metadata so existing local FileIO caching can reuse their bytes.

Scope

This is a read/core-only draft. The low-level codec can produce bytes for fixtures and callers, but Python manifest writers do not automatically create or publish sidecars in this PR. Writer, merger and failed-write cleanup changes are deferred to a follow-up. No Java cache changes are included.

Validation

• Python 3.11: 159 manifest/read/file-type tests passed.
• Python 3.6: all 91 focused sidecar/file-type tests passed with isolated dependencies. The broader suite has 133 passed, 9 skipped and 17 failures; the same 17 failures reproduce on unmodified master in the same environment (PyArrow 6 lacks Table.from_pylist / sort_by, and Lance is not installed).
• Shared Java v1 golden file: byte-for-byte encoding agreement and read selection checks passed.
• Python lint passed using the repository configuration.
• AST comparison confirms only read and read_entries_parallel changed in ManifestFileManager; all writer methods remain identical to master.

[XiaoHongbo-Hope]

+1

[JingsongLi]

+1