[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/ConfigureWifiSettings.java

@@ -69,7 +69,7 @@ public class ConfigureWifiSettings extends DashboardFragment {
 
     @Override
     protected List<AbstractPreferenceController> createPreferenceControllers(Context context) {
-        final WifiManager wifiManager = (WifiManager) getSystemService(WIFI_SERVICE);
+        final WifiManager wifiManager = getSystemService(WifiManager.class);
         final List<AbstractPreferenceController> controllers = new ArrayList<>();
         controllers.add(new WifiP2pPreferenceController(context, getSettingsLifecycle(),
                 wifiManager));