Update bubble bar stash and unstash animation

Bubble bar should stash and unstash from the handle.
Update the animation to match what is used for the taskbar animation.
Fix the stash handle reveal animation to animate the stash bounds to
bubble bar bounds and back.
This gives the effect of the handle morphing into the bubble bar and
bubble bar morphing back into the handle.

Bug: 345680453
Flag: com.android.wm.shell.enable_bubble_bar
Test: atest TransientBubbleStashControllerTest
Test: have bubbles in bubble bar and be in app, swipe up for taskbar and
  observe the bubble bar handle transforming into the bubble bar
Test: with taskbar and bubbles expanded, check that bubble bar
  transforms into the handle
Change-Id: I8508e9207092774cbdb990e65f7f84e56a924d0c