Iceberg encryption support

There are interests to bring Iceberg table encryption support in Polaris. Filing this issue to facilitate discussion.

Start by reviewing the Polaris repository and the discussion on this issue to determine the intended scope of Iceberg table encryption support. No files, tests, entry points, implementation plan, or acceptance criteria are identified in the issue, so the work is not ready to begin until those are established.

Written by the indexing model from the issue text.