DROP COMPACT STORAGE should invalidate prepared statements still using CompactTableMetadata

When we drop compact storage from a table, existing prepared statements continue to refer to an instance of CompactTableMetadata, rather than being invalidated so they can be assigned a new TableMetadata instance. There are perhaps some brute force ways to fix this, like bouncing the node, but that obviously sub-optimal.

One idea is to have TableMetadata#changeAffectsPreparedStatements() return true when we go from having to not having the DENSE flag. It should be pretty easy to validate a fix with a small addition to CompactTableTest.