Add Face Scanning anim

Render the face scanning animation and the camera
protection in FaceScanningOverlay, a SW layer.

Implementation notes:
  * The face scanning animation cannot be rendered
    in the HW layer because it requires color.
  * We cannot render the face scanning and camera
    protection overlays in different layers (HW and SW),
    because then they are difficult to coordinate.
 => Therefore, we render both the camera + face
    scanning animation in a SW layer together.

Test: atest ScreenDecorationsTest
Test: debug mode (adb shell setprop debug.screenshot_rounded_corners 1)
Test: enable color inversion, see camera protection is still black
Test: enable/disable face scanning feature and see that camera
  protection and face scanning anim works. Also test privacy dot
  indicator view still shows appropriately with and w/o the face
  scanning animation
Test: Check systemui dumpsys for view visibilities. Face
  scanning overlay should NOT be visible unless playing
  its animation.
Bug: 185128224
Change-Id: I2f67257bfcbfe177c76ebe76f20b1d1553e87175