Create a simple fallback activity for supervised user creation

Create a simple fallback activity to be started if no other activity could be
resolved when Add supervised user option is tapped in Multi User settings.

Bug: 207495450
Test: croot && make RunSettingsRoboTests -j40 ROBOTEST_FILTER="com.android.settings.users.UserSettingsTest"
Change-Id: I850a2798567787c2494c75aa5fa451ddf373410d
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 310ed38..c32406b 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -2964,6 +2964,12 @@
         </activity>
 
         <activity
+            android:name=".users.AddSupervisedUserActivity"
+            android:label="@*android:string/supervised_user_creation_label"
+            android:icon="@drawable/ic_settings_multiuser">
+        </activity>
+
+        <activity
             android:name="Settings$PaymentSettingsActivity"
             android:label="@string/nfc_payment_settings_title"
             android:exported="true"