Add logging for settings entrypoint to add supervised user.

Bug: 213442701
Test: croot && make RunSettingsRoboTests -j40 ROBOTEST_FILTER="com.android.settings.users.UserSettingsTest"
Change-Id: Ie6110b0ef5c16c9f83e3d939f78f21f003e55e35

src/com/android/settings/users/UserSettings.java

@@ -1251,7 +1251,10 @@ public class UserSettings extends SettingsPreferenceFragment
             }
             return true;
         } else if (pref == mAddSupervisedUser) {
+            mMetricsFeatureProvider.action(getActivity(), SettingsEnums.ACTION_USER_SUPERVISED_ADD);
+            Trace.beginSection("UserSettings.addSupervisedUser");
             onAddSupervisedUserClicked();
+            Trace.endSection();
             return true;
         } else if (pref == mAddGuest) {
             mAddGuest.setEnabled(false); // prevent multiple tap issue