Update dream manager to allow dreams while postured

Exposes a method in DreamManager for SystemUI to push the postured state
down into DreamManager. DreamManager can then take the postured state
and the user's settings preferences to determine if the device is
eligible to dream.

Bug: 383208131
Test: adb shell cmd statusbar device-postured true
Flag: android.service.dreams.allow_dream_when_postured
Change-Id: Ia7ea8b9657203b4c297b5d0d917c611dcb859cd4