Without modifying existing logic, animate out bubbles in reverse of the way they animate in.

Also, fixes a bug where the last bubble doesn't animate out because the stack view resizes before the animation completes.

This tries to do the same thing as ag/8943690 but without changing hasBubbles logic since that was causing issues.

Test: atest SystemUITests
Fixes: 134514227
Change-Id: I90893f1e510ebecbe26d77f2bdc0d2c9bb435548