Problem

Ancient append vec overflow was not being handled correctly with shrink_in_progress.
When we continue refactoring shrink, shrink_in_progress will be relied upon solely to determine which append vecs to drop from a slot.
This is tested by test_shrink_ancient_overflow. The test fails once we get rid of should_retain parameter from mark_dirty_dead_stores. At the moment, we are still relying on the append vec ids and should_retain to correctly remove old stores after a shrink.

Summary of Changes

Update shrink_in_progress correctly for ancient append vec overflow case.

Fixes #