Setup external/robolectric for SettingsRoboTests

Current failing tests: ab/I64100010182936387
Had to Ignore some of com.android.settings.accessibility tests, which will be fixed separately

Bug: 261728063
Test: atest SettingsRoboTests -- --test-arg com.android.tradefed.testtype.IsolatedHostTest:java-flags:-XX:CompressedClassSpaceSize=3g

Change-Id: I4a0cb992db924936826e0c9808accc78dddb5f30

tests/robotests/src/com/android/settings/users/UserSettingsTest.java

@@ -97,6 +97,7 @@ import java.util.List;
         ShadowUserManager.class,
         ShadowDevicePolicyManager.class,
         SettingsShadowResources.class,
+        com.android.settings.testutils.shadow.ShadowFragment.class,
 })
 public class UserSettingsTest {