Support burn-in for all transitions to/from AOD

This provides for smooth motion in all cases, such as
PRIMARY_BOUNCER->AOD. It also removes edge cases
in AodAlpha, and consolidates everything back in
KeyguardRootViewModel.

Also, move tests to multivalent

Fixes: 326636062
Test: atest com.android.system.keyguard.ui.viewmodel
Flag: ACONFIG com.android.systemui.migrate_clocks_to_blueprint
TEAMFOOD

Change-Id: I5f83d1594bbd29eaf427e4cad1a9a6156e37ee8c