We no longer support the "peeking" model where the shelf would
peek on motion pause from an app and overview would peek on motion
pause from home. Thus, removed/inlined the following:
- FlingAndHoldTouchController (merged into its sole subclass
NoButtonNavbarToOverviewTouchController)
- ShelfPeekAnim
- OverviewPeekState
Change-Id: I066a3ad2636fde4786089c922b896bf1e03361fd