Refactor UdfpsView into FrameLayout containing 2 views

1) Views are shown mutually exclusively.
2) No longer need to drawImmediately(clearRunnable) in stopIllumination,
   since the view is set to View.INVISIBLE
3) Moved setOnIlluminatedRunnable to startIllumination as a param

Fixes: 179080247

Test: atest com.android.systemui.biometrics

Change-Id: I7e94df165020401685c91922924724f142585832