Fix bubble added from the overflow background arrow animation.

The new bubble animation now uses a "selected location" argument to
position the pointing arrow.

Test: BubbleAnimatorTest
Test: Manual. Create a bubble bar with overflow. Open the overflow menu
and click an overflow bubble icon. Observe that a new bubble is added
and immediately expands. Observe that the arrow animates to the new
bubble's position.
Test: Manual. Create a bubble bar with overflow. Open any bubble.
Trigger a new bubble notification. Observe that a new bubble is added
but does not expand, so the arrow remains at the currently open bubble.
Flag: com.android.wm.shell.enable_bubble_bar
Fixes: 359952121

Change-Id: I47f5b6c2aad775f2dd3e70f8c544a3711f192342