2/n: Add default implementation for multi-biometric enroll

1) Adds a layout for multi-biometric selection in BiometricEnrollActivity
2) Adds widgets for checkboxes
3) Shows ConfirmLock*/ChooseLock* for multi-biometric devices in
   BiometricEnrollActivity
4) finish()'s when loses foreground
5) Adds default string for ChooseLock* and multi-biometrics, e.g.
   "Set up Password + Biometrics", as well as associated plumbing
   to bring the user back to BiometricEnrollActivity once the
   credential is enrolled
6) When max templates enrolled, checkbox becomes disabled and
   description string is updated

Bug: 162341940
Bug: 152242790
Fixes: 161742393

No effect on existing devices with the following:
Test: adb shell am start -a android.settings.BIOMETRIC_ENROLL
Test: SUW
Test: make -j RunSettingsRoboTests

Exempt-From-Owner-Approval: Biometric-related change
to EncryptionInterstitial

Change-Id: I855460d50228ace24d4ec5fbe330f02ab406cc02

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

@@ -236,7 +236,7 @@ public class FaceSettings extends DashboardFragment {
     public void onActivityResult(int requestCode, int resultCode, Intent data) {
         super.onActivityResult(requestCode, resultCode, data);
 
-        if (mToken == null && !BiometricUtils.containsGatekeeperPassword(data)) {
+        if (mToken == null && !BiometricUtils.containsGatekeeperPasswordHandle(data)) {
             Log.e(TAG, "No credential");
             finish();
         }