Show policy transparency dialog if adding Wi-Fi config is not allowed

- When the user is restricted by UserManager.DISALLOW_ADD_WIFI_CONFIG, clicking on a Wi-Fi network will show the Settings policy transparency dialog.

- The "Not allowed by your organization" summary in Wi-Fi networks will be removed in a separate CL.

Bug: 233871529
Test: manual test
make RunSettingsRoboTests ROBOTEST_FILTER=Wifi

Change-Id: Ia978be8e85a5809de1331f3e0edc11fbc8925c80

tests/robotests/src/com/android/settings/wifi/LongPressWifiEntryPreferenceTest.java

@@ -36,8 +36,10 @@ import org.mockito.Spy;
 import org.mockito.junit.MockitoJUnit;
 import org.mockito.junit.MockitoRule;
 import org.robolectric.RobolectricTestRunner;
+import org.robolectric.annotation.Config;
 
 @RunWith(RobolectricTestRunner.class)
+@Config(shadows = ShadowRestrictedPreference.class)
 public class LongPressWifiEntryPreferenceTest {
 
     @Rule