Running various lifecycle-related tests on main thread

- Latest AndroidX drop changes the requirements for observers
  which must be registered on the main thread

Bug: 162884675
Test: atest SystemUITests passes locally
Change-Id: Ib77248bc6d44cc9c8a5d2ad0e5c95feab6a54a01
Merged-In: Ib77248bc6d44cc9c8a5d2ad0e5c95feab6a54a01
(cherry picked from commit 5676d9888174954c8f9b624110d5f1d6016cf82b)
7 files changed