feat(transaction): add ManageSnapshotsAction for snapshot refs. (#1939)

[hippalus]

Which issue does this PR close?

• Closes Add the ability to transactionally create named references (tags) to a snapshot in the FastAppendAction #1939.

What changes are included in this PR?

Adds ManageSnapshotsAction, a transaction action for managing branches and tags (like Java's ManageSnapshots). PR1 of #1939 ref management only, no rollback/set-current-snapshot/cherrypick.

Transaction::manage_snapshots() supports:

• create_branch / create_tag
• remove_branch / remove_tag
• rename_branch
• replace_branch (by id) / replace_branch_with_ref (by ref) / replace_tag
• fast_forward_branch
• set_min_snapshots_to_keep / set_max_snapshot_age_ms (branch-only) / set_max_ref_age_ms

Notes:

• Validation runs at commit time, against a working copy of the refs map (chained ops see intermediate state).
• Updates/requirements are diff-based against the current refs, net no-ops emit nothing, concurrent ref changes are caught via RefSnapshotIdMatch.
• Reuses existing SetSnapshotRef/RemoveSnapshotRef + UuidMatch/RefSnapshotIdMatch no new variants.

Supporting changes:

• TableMetadata::refs() and snapshot_reference() accessors.
• util::snapshot::is_ancestor_of() (used by fast-forward).
• TableMetadataBuilder::set_ref() rejects setting main to a tag (Java parity).

Are these changes tested?

Yes unit tests in manage_snapshots.rs, following the expire_snapshots.rs style:

• One test per operation plus its failure cases (missing/duplicate refs, wrong ref kind, removing/renaming main, non-ancestor fast-forward, negative retention, …).
• Diff/requirement behavior: minimal diffs from chained ops, transient refs get no requirement, source-ref concurrency assertions, round-trip through TableMetadataBuilder.
• The main-as-tag rejection is covered by a test in table_metadata_builder.rs.