[python] Support snapshot properties in table commits

[YannByron]

Summary

PyPaimon can deserialize Snapshot.properties, but its table commit API has no way to populate them. Java supports the same capability through ManifestCommittable.addProperty. This PR closes that gap so Python applications can atomically publish recovery or checkpoint state with the data represented by the snapshot, instead of maintaining an inconsistent sidecar.

The direct LeRobot capture writer in #9665 is the first consumer: it uses the properties to resume global frame, episode, and task indices without scanning the table.

Changes

• Add an optional snapshot_properties mapping to batch and stream table commits.
• Preserve the properties through append, overwrite, conflict retry, and snapshot creation.
• Keep existing callers unchanged when the argument is omitted and serialize an empty mapping as no snapshot properties, matching Java behavior.

Testing

• Batch commits persist the supplied properties in the latest snapshot.
• Stream commits persist checkpoint properties in the latest snapshot.
• Batch, stream, and overwrite paths forward the properties to the file-store commit layer.
• python -m pytest -q pypaimon/tests/table_commit_test.py pypaimon/tests/table/simple_table_test.py (28 passed).
• Ruff and git diff --check pass for all changed files.

Notes

An empty append still does not create a snapshot solely for properties. This PR adds properties to snapshots produced by data commits; it does not add metadata-only commits.

Related: #9665

[JingsongLi]

+1