Move several content observer registrations to background

Moves several content observer registrations to background using new
async APIs to prevent content observer jank.

Bug: 327558308
Flag: com.android.systemui.register_content_observers_async
Test: built, unit tested, checked panther
Change-Id: I748b645b57480442664fba0a7d1e366d5c30c233
3 files changed