Add support for more transitions

For both notifications and keyguard, apply alpha transition values
from more edges in the tranistion graph.

Also, make sure SharedNotificationContainerViewModel is a singleton.

Also, slightly adjust the delay from ALTERNATE_BOUNCER. A pending
refactor will fix this for good.

Fixes: 322159440
Test: manually run through LOCKSCREEN->*->GONE cases and look for any
visible flickers on any elements
Flag: ACONFIG com.android.systemui.keyguard_shade_migration_nssl
DEVELOPMENT

Change-Id: I2e3f2fc47ca2abb3ce7717e47235cbbf7debbcb9