Update PIP dismiss to show scrim + info text at the bottom of the screen

- Rather than testing how far off screen the PIP is, instead tests how far
  past the nav bar / on screen bars the PIP is to determine if it is a
  dismiss
- When dragging PIP around screen, display info text + scrim at bottom
  these are above the PIP in z-order
- On lift up or when PIP is dismissed, info text + scrim also hide
- Alters dismiss animation to use end point on trajectory of finger and
  use FlingAnimationUtils when flinging

Test: Drag PIP around screen, notice dismiss scrim + text appear, dismiss
      PIP and scrim / text also disappear
Bug: 35358628
Change-Id: Ibc0f6a884903f7d1b3ca2fd5c20647b4acf15a71