[iceberg] Support TagCallback.notifyCreation without snapshot id

[ArnavBalyan]

Purpose

• notifyCreation(String) throws UnsupportedOperationException breaking the TagCallback contract.
• The snapshot id is available to the iceberg compat layer, TagManager persists the tag file before invoking a callback.
• Ensure we can support Tagmanager notify creation based on the tag id.

Tests

• UT

[ArnavBalyan]

cc @JingsongLi thanks :)