4/n: Add basic enrollment for Face

Bug: 110589286

Test: fingerprint enrolling still works
Test: enrollment flow with and without a pin set up still works properly
Test: enrollment continues when configuration changes, stops otherwise

Change-Id: I39f76c7f1a16e9533cef573f87cf4b81cb20cb18

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

@@ -113,8 +113,8 @@ public class FaceEnrollIntroduction extends BiometricEnrollIntroduction {
     }
 
     @Override
-    protected Intent getFindSensorIntent() {
-        return null; // TODO
+    protected Intent getEnrollingIntent() {
+        return new Intent(this, FaceEnrollEnrolling.class);
     }
 
     @Override