Revert ESP-MQTT (#508)

* Revert ESP-MQTT

* Revert ESP-MQTT

* Update sdkconfig.defaults

lib/espMqttClient/test-coverage.py

@@ -0,0 +1,22 @@
+import os
+
+Import("env", "projenv")
+
+# Dump build environment (for debug purpose)
+print(env.Dump())
+
+# access to global build environment
+print(env)
+
+# access to the project build environment
+# (used for source files located in the "src" folder)
+print(projenv)
+
+def generateCoverageInfo(source, target, env):
+    for file in os.listdir("test"):
+        os.system(".pio/build/native/program test/"+file)
+    os.system("lcov -d .pio/build/native/ -c -o lcov.info")
+    os.system("lcov --remove lcov.info '*Unity*' '*unity*' '/usr/include/*' '*/test/*' -o filtered_lcov.info")
+    os.system("genhtml -o cov/ --demangle-cpp filtered_lcov.info")
+
+env.AddPostAction(".pio/build/native/program", generateCoverageInfo)