Incorporate Falsing Belief sooner.

Process gestures in the FalsingManager as soon as they complete,
instead of waiting for the next gesture to begin.

This provides more accurate and useful feedback about falsing belief.
It means that a falsing "event" will be fired as soon as the indicated
threshold is crossed, instead of on the next, possibly intentional
gesture.

Bug: 184042853
Test: atest SystemUITests && manual
Change-Id: Idd9227de3a03c52dabe31f52dbb45ff890615ded