Fix issues with animations when the stack is expanded.

- Don't show the flyout if the stack has become expanded.
- Add onChildReordered so that the controllers don't receive onChildAdded calls when views are reordered. This was causing animation issues with expanded bubbles.
- Clear the dragging out bubble onGestureFinished, so that it's not ignored by animations.
- Update the expand/collapse animations when a new child is added during animation, so that it'll also animate to the proper spot.

Fixes: 129370170
Bug: 123542488
Test: atest SystemUITests
Change-Id: I1360deb09db82bd3ba72cb91fc9abe05b6dc1a9c