Animate bubble badge scale

When a bubble is added or removed while we're collapsed, animate the
badge scale to make sure that only the badge for the top bubble is
visible.

Flag: com.android.wm.shell.enable_bubble_bar
Fixes: 360652359
Test: manual
       - add bubble while collapsed
       - observe that badge only shows for top bubble
       - remove bubble while collapsed
       - observe that badge only shows for top bubble
Change-Id: I91472bb2ddeeeebd33ca64e20e065b2336c08589