Before, when the organizer binder died, it will trigger TaskFragment
removal that can cause surface placement. Now, we make sure to cleanup
all pending events before removing organized TaskFragments.
Bug: 251583070
Bug: 254322068
Test: atest WmTests:TaskFragmentOrganizerControllerTest
Change-Id: Ifec6f763a7e7819c93cc28d71bd0314f3ac9ac0d