Make the flyout dismissable with a gesture.

This adds the flyout-to-dot transition, and encapulates the flyout logic in a custom view. This also adds support for the 'new' dot changing sides (previously unimplemented) and animates it changing sides when the stack changes sides.

Test: atest SystemUITests
Fixes: 129768381
Bugs: 129768381
Change-Id: I90697b437cf14e5c5a211c87ed2c131a12e697e7