Tune Assistant Gesture

=> bumping detectable region to 48 dp horizontal + vertical within corner
=> centering detectable angle;  total 70 degrees (ie. btw 10 off the vertical and 10 off the horizontal)
=> pilfering touch events when slop is passed and assistant gesture is engaged
=> Fixing issue where we were incorrectly using “sharedState” causing incorrect handling of gestures subsequent to AssistantTouchConsumer being invoked (it was forgetting to clear it’s input state and hence reporting “active” when it wasn’t). The symptom was that gestures after the AssistantTouchConsumer would never actually move the active window even though state was being updated; you’d feel the Overview haptic.
=> Devices with large corner radii are still somewhat problematic as the initial touch down often lands high on the display (ie. above the 48 dp region).

Change-Id: I3d5761112f4cb8b7b1eee987de5afe9aee260304