Rewrite long swipe resistance ("pullback") logic

- Rename "pullback" to "resistance" to reduce confusion.
- Remove mDragLengthFactorStartPullback & mDragLengthFactorMaxPullback
- Add AnimatorControllerWithResistance, which has 2 controllers, one
  for the normal shift to overview, then one to apply the resistance
  when swiping beyond that.
- Don't hack animator interpolators/progress; insteaad, allow progress
  to go > 1 (which will run the separate resistance animator).
- Don't start launcher controller separately from window controller;
  instead, both are controlled by mCurrentShift in updateFinalShift().
- The resistance animation logic is shared by both the active window
  and launcher (RecentsView).

Bug: 149934536
Change-Id: Ib0f9da18e10cc9ddf1a2f82ed767f237c89d3a41
Merged-In: Ib0f9da18e10cc9ddf1a2f82ed767f237c89d3a41