Biometrics v2 RFPS enrolling refine

1. Fix back key in enrolling page
2. Fix 0.5 sec black screen if user presses skip

Bug: 260957939
Test: atest FingerprintEnrollmentActivity
Change-Id: If5308246ed380c2e3dd12f19f13aa38fc8c178a8

src/com/android/settings/biometrics2/ui/view/FingerprintEnrollEnrollingUdfpsFragment.java

@@ -107,7 +107,7 @@ public class FingerprintEnrollEnrollingUdfpsFragment extends Fragment {
     private boolean mIsAccessibilityEnabled;
 
     private final View.OnClickListener mOnSkipClickListener =
-            (v) -> mEnrollingViewModel.onSkipButtonClick();
+            (v) -> mEnrollingViewModel.onCancelledDueToOnSkipPressed();
     private final Observer<EnrollmentProgress> mProgressObserver = progress -> {
         // TODO
     };