feat: Add Set Current Snapshot to ManageSnapshots API

[geruh]

Rationale for this change

This PR adds the ability to change the set the current snapshot of a table. A bulk of this work was done in #758 but instead we have broken it out to focus on the set snapshot logic first. Additionally I added a few more tests, following the existing expire snapshots behavior.

Are these changes tested?

Yes, added tests

Are there any user-facing changes?

New API :)

table.manage_snapshots().set_current_snapshot(snapshot_id=123456789).commit()


table.manage_snapshots().set_current_snapshot(ref_name="my-tag").commit()

# chaining
table.manage_snapshots() \
      .create_tag(snapshot_id=older_id, tag_name="my-tag") \
      .set_current_snapshot(ref_name="my-tag") \
      .commit()

[geruh]

We can rip this helper out of transaction and leave in managesnapshots api.