Fix new lightreveal transition

- Lightreveal will now play independently instead of being directly tied
to Transition steps. This is needed because the transition AOD => GONE
has actually two parts of the transition AOD => LOCKSCREEN then
LOCKSCREEN => GONE would otherwise cancel the animation when the second
part of the transition starts.
- LightReveal will now play backwards from it's current state when
unlocking/locking quickly one after another (instead cancel/restart)
- LightReveal will now play correctly (from tap) when AOD has not yet
entered low power mode
- Power off will now animate correctly even if the device was unlocked
with tap

Test: added unit tests
Bug: b/292087855

Change-Id: Ie25efca4a829dede2da80a518e425ec9f314d6d9