Animate the bubble badge

The bubble badge now scales together with the expand and collapse
animation of the bubble bar. The badge for the selected bubble is
always kept at full scale.

Flag: com.android.wm.shell.enable_bubble_bar
Fixes: 349826874
Test: manual
       - create some bubbles in the bubble bar
       - expand and collapse the bar
       - observe badge icons scale accordingly
Change-Id: I04e9174f4a921e404cb3162337f594c16478b16c