[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/wifi/WifiNoInternetDialog.java

@@ -107,7 +107,7 @@ public class WifiNoInternetDialog extends AlertActivity implements
             }
         };
 
-        mCM = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
+        mCM = getSystemService(ConnectivityManager.class);
         mCM.registerNetworkCallback(request, mNetworkCallback);
 
         final NetworkInfo ni = mCM.getNetworkInfo(mNetwork);