Only send bubble bar top coordinate to shell

Stop sending entire bubble bar bounds to shell.
Keeping the bounds in sync was error prone as bubble bar can expand and
collapse. Bubbles can be added/removed.
In each of these cases we had to make sure that shell gets updated.
Shell only needed the full bounds for collapse/expand animation. But
after updating the animation, shell only needs the top coordinate of the
bubble bar.

Bug: 330585402
Flag: com.android.wm.shell.enable_bubble_bar
Test: bubble bar drag
  - drag bar from right to left
  - expand the bar
  - check that expanded view scales in from left edge
  - collapse and drag bar back, check the animation
Test: selected bubble drag
  - drag expanded bubble from right to left
  - check that expanded view scales in from the left edge
  - drag the bubble back to right, check animation
Test: other bubble drag
  - drag a unselected bubble from right to left
  - check that the selected bubble expands in from left edge
  - drag the bubble back to right, check animation again
Test: drag bubble from right to left, observe that expanded view
  expand animation originates from the bubble bar

Change-Id: Ib66cef8d3c04bce54a69e30e99edd408a31f018f