Add transaction actions for managing snapshot branches and tags

### Is your feature request related to a problem or challenge?

iceberg-rust already provides typed snapshot references and the underlying
`SetSnapshotRef`, `RemoveSnapshotRef`, and `RefSnapshotIdMatch` primitives,
but does not currently expose a public transaction action for standalone
branch and tag management.

In a table-management CLI, we need to create tags on existing snapshots,
rename or delete references, and move branch heads through the existing
`Transaction` and `Catalog` APIs. We would prefer to keep reference-update
semantics in iceberg-rust rather than implement custom catalog commits
in the application.

Previous related work: #1298 proposed branch/tag operations through
`ManageSnapshots` and was closed due to inactivity.

This is related to, but distinct from, #1939: that issue requests tagging
the snapshot generated by `FastAppendAction` within the same transaction.
This request concerns managing references to existing snapshots.

### Describe the solution you'd like

Add a snapshot reference action to the existing `Transaction` API, using
the typed `SnapshotReference` and `SnapshotRetention` types.

The action should support creating and deleting branches and tags,
renaming references atomically, fast-forwarding branches, and resetting
branch heads to existing snapshots. It should preserve retention policies,
protect `main` from deletion or rename, and reject attempts to create a
reference whose name is already in use.

Reference updates should use the existing `TableUpdate` and
`TableRequirement` primitives. Concurrent head changes should produce a
conflict rather than silently overwrite another writer's changes.

I have a preliminary implementation exposed through
`Transaction::update_snapshot_references()`, with tests for validation,
atomic rename, conflicts, retries, and catalog round trips. It follows the
current transaction-action structure rather than adding management logic
to the snapshot metadata types.

### Willingness to contribute

I would be willing to contribute to this feature with guidance from the Iceberg Rust community

Start with the existing Transaction API and the preliminary Transaction::update_snapshot_references() implementation, then review the typed SnapshotReference and SnapshotRetention types plus the TableUpdate and TableRequirement primitives. Use the mentioned validation, atomic rename, conflict, retry, and catalog round-trip tests as guides. Done means reference creation, deletion, renaming, fast-forwarding, and resetting work atomically while preserving retention and rejecting protected or conflicting updates.

Written by the indexing model from the issue text.