move code to handle network events from anonymous to class method

src/networkDevices/EthernetDevice.h

@@ -67,6 +67,7 @@ private:
     void init();
     void onDisconnected();
     void waitForIpAddressWithTimeout();
+    void onNetworkEvent(arduino_event_id_t event, arduino_event_info_t info);
 
     bool _connected = false;
     bool _restartOnDisconnect = false;