Add generic support for corner radius in launch animations.

This CL adds a generic way in GhostViewLaunchAnimationController to
change the corner radius of the expanding background. It does so by
supporting Gradient- and LayerDrawable (and therefore RippleDrawable).

This will be first used to animate the launch of the settings after long
clicking a QS tile (see ag/13988954), but this implementation will
hopefully work with other views as well.

This CL also adds the wiring in ActivityStarter that will be needed by
the QuickSettings.

Bug: 184121838
Test: Manual
Change-Id: I40f7048edd682d5d68c32b4439368d19009a8df1