Use isDreaming signal for Gone->Dream transition

Power button press over launcher sometimes(apps drawer open)
causes keyguard clock to briefly appear. The transition is
Gone->Lockscreen->Dream instead of Gone->Dream due to
isAbleToDream's 500ms delay.

Directly using isDreaming for Gone->Dream fixes the issue and
should be safe as isAbleToDream is intended for delay checking
dreaming info after exiting AOD. And powerInteractor.asleep
arrives early and triggers Gone->AOD correctly when AOD enabled.

Fixes: b/372563526
Flag: EXEMPT bugfix
Test: verify dream/doze/AOD transition by pressing power button over launcher
Change-Id: I8c81eb2e08ba89c935dd9e496a0ad92260fa3b4d