Flexible bubble sizing & fixed position

This will enable some stuff for taskbar & hopefully make customizations by
ARC++ easier??

- BubblePositioner now tracks the size of the bubble & bitmap within it.
  Have to use a multiplier to derive the size of a couple of things now
  (e.g. bitmap size)
- BubblePositioner now tracks the position of the bubble stack & allows
  a way to override / set a fixed position. If something is in fixed
  location, it is not draggable (however when expanded you can still
  drag individual bubbles to dismiss)
- BubblePositioner tracks some taskbar related info
- Rather than checking for "isLandscape" we want "showBubblesVertically"
  (e.g. device might not be landscape but should be vertical if taskbar)
- Fixes an animation issue where bubbles super-overshoot the y position
  when expanding vertically.

Bug: 167413172
Test: a lot of manual testing
Test: atest WMShellTest SystemUITests
Change-Id: I79948a4bd6b58fb3aa2f52e2553f3dfc31630cf1