Introduce BubbleBarExpandedView

* Adds the new BubbleBarExpandedView & basic HandleView classes for
  rendering a bubble's expanded view when bubbles are in the bubble
  bar.

* The HandleView class will eventually render the manage menu
  but this is not implemented yet.

* Adds BubbleBarExpandedView to BubbleViewProvider & Bubble, this will
  be a nullable view that is only inflated when the bubble bar is
  active. The inflation / creation of this view is done in a separate
  CL.

Test: treehugger / manual with other CLs
Bug: 253318833
Change-Id: Iee05e39fc7c06f5210c0adccbe69ba6991e722df