Scale bubble bar to the width of the handle

When animating bubble bar from the stash handle, scale the width to the
handle.
Bubble bar is already almost the size of the handle, but a small scale
is still added.

Bug: 345488489
Flag: com.android.wm.shell.enable_bubble_bar
Test: atest TransientBubbleStashControllerTest
Test: slow animations down and unstash and stash bubble bar, observe
  that the width of the bubble bar scales down to the handle
Change-Id: I54dc228fa41d4d494bfb15e191d2ba563c0970c7