Send dream state updates through DreamManagerStateListener.

This changelist extends DreamManagerStateListener to also send updates
about the dream state, including when the dream started and stopped.
This allows system server components to receive state updates without
needed to listen to the dream state broadcasts.

Test: atest DreamControllerTest#startDream_dreamListenerNotified
Test: atest DreamControllerTest#stopDream_dreamListenerNotified
Bug: 275108597
Change-Id: Ifb1e1266b938d50e0744aa106557c8c7db52f442