Adds DynamicAnimation-based movement to the bubbles.

See go/bubble-stack-design for a high level overview of these changes. This is a large CL, but required in order to allow continued development and team testing without breaking functionality over the course of multiple CL submissions.

To integrate the new animations, the following changes have been made to existing code:
* (BubbleStackView) The bubble container (and thus, the stack view) are MATCH_PARENT to allow the bubbles to independently translate anywhere on the screen.
* (BubbleStackView) Start position is set by the stack controller, not BubbleStackView.
* (BubbleStackView) Expand positon is set by the expansion controller, not BubbleStackView.
* (BubbleStackView/BubbleTouchHandler) Added the methods onDragStart/onDragged/onDragFinish, and onBubbleDragStart/onBubbleDragged/onBubbleDragFinish, for cleaner dispatch of touch events to the appropriate animation controller.
* (BubbleStackView/BubbleController) The stack view's getBoundsOnScreen returns the first bubble's bounds, if the stack is not expanded.
* (BubbleStackView) applyCurrentState no longer manages translation of bubbles, or the expanded view, these are controlled by animation.
* (BubbleMovementHelper) Deleted, no longer needed.
* (Everywhere) Changed uses of Point to PointF, since translation values are floats anyway.

Known issues to be fixed in subsequent, far smaller CLs:
* (b/123022862) Bubble dragging out/dismissing is not animated, and the bubbles can be deposited anywhere. Tap outside the stack to collapse them back to normal.
* (b/123023502) New bubbles added while the stack is expanded are not positioned properly.
* (b/123022982) Expanded view arrow is sometimes in the wrong position.
* (b/123023410) If the stack is expanded while animating, it collapses to its original position even if not along the edge of the screen.
* (b/123023904) The expanded view doesn't animate out, it disappears instantly.
* (b/123026584) Bounds in landscape are a bit wonky.

Bug: 111236845
Test: atest SystemUITests
Test: physics-animation-testing.md
Change-Id: Icaca09e5db89c635c9bb7ca82d7d2714362e344e