refactor NetworkDevice interface to work with new esp mqtt lib

networkDevices/espMqttClientEthernet.cpp

@@ -0,0 +1,8 @@
+#include "espMqttClientEthernet.h"
+
+espMqttClientEthernet::espMqttClientEthernet(uint8_t priority, uint8_t core)
+: MqttClientSetup(true, priority, core),
+  _client()
+{
+    _transport = &_client;
+}