Implement different thresholds for entering and exiting posturing

Simply tapping the screen while the device is on a dock might cause
enough movement to dip the confidence below the 0.8 threshold. This
currently causes the device to exit the postured state. To account for
this, we now implement different thresholds for entering and exiting the
state. The confidence needs to be high to enter (0.8f) - but as long as
the confidence remains above 0.5f then we will not exit the state. This
allows the phone to move slightly while postured without exiting.

This change also refactors some of the logging and batches updates with
a small debounce delay to reduce log noise.

Fixes: 413035192
Test: atest PosturingInteractorTest
Flag: android.service.dreams.allow_dream_when_postured
Change-Id: Id29cc77489eba6e7c1357c4d284efbcf7262df43