Restores the exit-pip activity back to overlay container

- Restoration happens if the original associated activity
  is still the top-most activity behind the overlay
  activity/container.
- Recreate the overlay container when needed.

Bug: 297887697
Test: launch overlay, enter and exit pip
Test: atest OverlayPresentationTest
Flag: com.android.window.flags.fix_pip_restore_to_overlay
Change-Id: I6f11b6a24302e21cc8b7198a4856b6ce17aae0eb