Adjust ConfirmDeviceCredentialActivity system bars

CDCA is a transparent activity with the sole purpose of
requesting authentication. Since authentication is all drawn
by SystemUI, we should also stop this activity from drawing
the StatusBar.

Register to receive biometric system events (early user canceled),
so that we can finish() and start the activity transition
simultaneously. This fixes some navigation bar jank.

Bug: 148273355

Test: Set up a work profile, then install BiometricPromptDemo
      Disable one-lock and set up a password/biometric for the
      work profile. Lock/unlock screen, then open the work
      profile version of the app. No status bar jank seen.
Change-Id: I54a352527ed007dcaf1bea14a51711e4022fe028

src/com/android/settings/password/BiometricFragment.java

@@ -77,6 +77,13 @@ public class BiometricFragment extends InstrumentedFragment {
                 mClientCallback.onAuthenticationFailed();
             });
         }
+
+        @Override
+        public void onSystemEvent(int event) {
+            mClientExecutor.execute(() -> {
+                mClientCallback.onSystemEvent(event);
+            });
+        }
     };
 
     private final DialogInterface.OnClickListener mNegativeButtonListener =
@@ -121,10 +128,6 @@ public class BiometricFragment extends InstrumentedFragment {
         }
     }
 
-    boolean isAuthenticating() {
-        return mAuthenticating;
-    }
-
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
@@ -144,7 +147,8 @@ public class BiometricFragment extends InstrumentedFragment {
                 .setConfirmationRequired(mBundle.getBoolean(
                         BiometricPrompt.KEY_REQUIRE_CONFIRMATION, true))
                 .setDisallowBiometricsIfPolicyExists(mBundle.getBoolean(
-                        BiometricPrompt.EXTRA_DISALLOW_BIOMETRICS_IF_POLICY_EXISTS, false));
+                        BiometricPrompt.EXTRA_DISALLOW_BIOMETRICS_IF_POLICY_EXISTS, false))
+                .setReceiveSystemEvents(true);
 
         mBiometricPrompt = builder.build();
         mCancellationSignal = new CancellationSignal();