Fix new Expandable animation lag

This CL ensures that the new implementation of the Compose Expandable is
drawing the expandable inside the dialog overlay during dialog launches,
rather than in the Expandable overlay. See b/397904604#comment6 for
details and before/after videos.

Bug: 397904604
Test: Manual
Flag: com.android.systemui.qs_ui_refactor_compose_fragment
Change-Id: I691d17a9c3c8deb74484b744bb40a4a93812bf7d