[python] Generate manifest sidecars on writes

[leaves12138]

Purpose

Extract the remaining PyPaimon writer integration from #9743. This builds on the merged v1 codec/block-pruned reader in #9908 and the manifest-reference retry fix in #9921; it does not change the sidecar format or Java implementation.

• Generate sidecars for ordinary and rolling manifest writes, including manifests produced by minor compaction.
• Publish _EXTRA_FILES only after both immutable outputs close successfully. manifest.sidecar.enabled controls reads and writes and continues to inherit manifest-sort.enabled when unset.
• Clean up newly created manifest/sidecar pairs on write or preparation failure, including previously completed rolling outputs. Preserve existing manifests and propagate cancellation. Commit outcomes that may be uncertain keep the existing no-cleanup behavior.
• Keep coarse RowID bounds unknown for invalid ranges, consistent with sidecar coverage.
• Document writer behavior and exercise the real writer in the existing pruning tests.

Tests

• Python 3.11: 276 passed across manifest, commit/retry, explain, cache, file-type, and bucket-pruning suites.
• Python 3.6: 116 passed across sidecar, block-index, and file-type suites.
• Flake8 passed with paimon-python/dev/cfg.ini; git diff --check passed.
• Added coverage for explicit disablement, write/close failures, interruption, rolling cleanup, commit cleanup ownership, and invalid RowID bounds.
• Additional isolated Python-write/Java-read check: 12 manifests, 1,806 entries, null/deflate/Zstandard compression, ordinary and rolling outputs, an empty manifest, and 108 block-pruned read comparisons all matched the full Java reads.

PYTHONPATH=paimon-python python -m pytest \
  paimon-python/pypaimon/tests/manifest \
  paimon-python/pypaimon/tests/file_store_commit_test.py \
  paimon-python/pypaimon/tests/read_builder_explain_test.py \
  paimon-python/pypaimon/tests/caching_file_io_test.py \
  paimon-python/pypaimon/tests/file_type_test.py \
  paimon-python/pypaimon/tests/pushdown_bucket_test.py -q