Swipe up to go home, swipe and hold to go to overview

- Pause (swipe and hold) detection based on velocity and acceleration,
  so it feels immediately responsive
- Don't show shelf during swipe; peek when swipe pauses
- Disallow long swipe
- If swiping to go home (we didn't detect a pause), animate window and
  launcher together (not final animation, but mechanism is in place)
- Guarded by SWIPE_HOME flag

Bug: 111926330
Change-Id: Ie4af04517c6688e3d649c2971a1aad197837cb3b