Only cancel the recents anim upon visible stack order change

- We previously canceled the animation for all stack order changes,
  but if we keep an activity running while in Recents, then there
  are transparent changes (ie. when a task is dismissed) where we
  don't want to trigger the current recents animation to be canceled.

  If the change is from a stack that is not visible, then keep the
  current animation running.

Bug: 120426277
Test: atest WmTests:RecentsAnimationTest

Change-Id: I7d57999cc5f249ccfcc2f9d0a198385524024a67