Add the preference controller to control accessibility button preview preference

* Create FloatingMenuLayerDrawable class to handle the preview layer drawable

cherry picked from commit 60301476

Bug: 173940869
Test: atest AccessibilityButtonPreviewPreferenceControllerTest FloatingMenuLayerDrawableTest
Change-Id: Ia3d030547b377e87c505b2310f559f7f3876ecd5
Merged-In: Ia3d030547b377e87c505b2310f559f7f3876ecd5