Enable super smooth GONE->AOD (canceled)->LOCKSCREEN transitions

This adds special logic for notifications, which should not be visible
on AOD but need to fade in nicely once AOD->LOCKSCREEN starts.

Also, minor cleanup for transitions to start from their current value

Bug: 322198222
Fixes: 322197793
Test: atest com.android.systemui.keyguard
Flag: ACONFIG com.android.systemui.migrate_clocks_to_blueprint
DEVELOPMENT

Change-Id: Ic60430b1fe5ea15821f6fa00cd05c4aaa9863662