[flexiglass] Hydrate dozeAmount with AOD and DOZE transitions

Previously dozeAmount was updated based on a flow of AOD transitions,
which we converted to callbacks, which we converted back to a flow.
The flow-callback-flow conversion was working, but reacting only to AOD
transitions was not enough, because device is still dozing while it is
in low-power mode and nothing is displayed (KeyguardState.DOZING).

This was leaving the dozeAmount at `0` while KeyguardState.DOZING was
happening, which caused the NSSL to show the full Notification Stack,
while a Notification was Pulsing.

This CL moves determining the dozeAmount to KeuguardInteractor, and
hydrates it with DOZE, and AOD transitions.

Fixes: 363981730
Test: manual: check Pulsing and AOD Notifications
Flag: com.android.systemui.scene_container
Change-Id: I5b64ce7e0518d342f2acc5d31cf8d9f662178ca4