Adding support for nested LayerDrawables in GhostedViewLaunchAnimatorController

Currently we're assuming LayerDrawable will only contain GradientDrawables but that's not the case for QS tiles.

Fixes: 316773326
Test: Set device to dark theme -> long press dark theme tile to launch settings -> see corners of transitions are not colored
Flag: None

Change-Id: Ideaea10ab26af0325300ed4eb3a975e53273c22a