Consolidate face enroll intro/consent screens

Updates the UI of the face enroll intro screen based on the latest
mocks, while still allowing strings to be overlaid depending on the
device and/or face auth implementation.

Test: Manually tested face enrollment

Bug: 187207438
Change-Id: I5d912261b1eecfc7a241d6b48d549c4ff253ecdf

src/com/android/settings/biometrics/face/FaceStatusPreferenceController.java

@@ -68,7 +68,7 @@ public class FaceStatusPreferenceController extends BiometricStatusPreferenceCon
 
     @Override
     protected String getEnrollClassName() {
-        return mContext.getResources().getString(R.string.config_face_enroll_introduction);
+        return FaceEnrollIntroduction.class.getName();
     }
 
 }