Apply spring forces to animate to the final position for swipe home

Now instead of an incorrect hack that simulated accelerating to the target,
we actually apply spring forces to make it feel realistic and work no matter
where the target is.

Added two helper classes for this:
- FlingSpringAnim handles the fling, applying friction until reaching the target,
  then a spring to pull towards the final position (also applies if fling wasn't
  in the right direction or strong enough to reach the target).
- RectFSpringAnim uses 2 FlingSpringAnims (x + y) to animate from a starting rect
  to a target rect. It also has an animation to scale from the start rect to the
  target rect, sending progress update callbacks to the caller.

Bug: 123900446
Change-Id: Iafa89db1d55c42816acfa9f1bb84a7519b69ff12