Modify SwipeDismissLayout to perform its own exit animation

Instead of relying on the window animation system, in the special
case of a swipe-dismiss, disable any default window exit animation
and perform a custom animation. This bypasses some bugs in the
window animator codebase and allows us to have a nice "rebound"
animation if the user doesn't swipe far/fast enough to trigger a
dismiss.

Bug: 33041168
Change-Id: Ied45700d35a59950bacef1ba0650eaa5bc60fadb