[Settings] Support getSystemService(Class<T>)

Add getSystemService(Class<T>) to align the capability with framework
part.

This is a back port from aosp/1639943, aosp/1645152 and aosp/1648047

Bug: 179640862
Test: local
Change-Id: I035db55a71f94000ca35f8d71f03c19208423c73

src/com/android/settings/deviceinfo/firmwareversion/FirmwareVersionDetailPreferenceController.java

@@ -49,7 +49,7 @@ public class FirmwareVersionDetailPreferenceController extends BasePreferenceCon
 
     public FirmwareVersionDetailPreferenceController(Context context, String key) {
         super(context, key);
-        mUserManager = (UserManager) mContext.getSystemService(Context.USER_SERVICE);
+        mUserManager = mContext.getSystemService(UserManager.class);
         initializeAdminPermissions();
     }