Set the AP name with the short name plus the 4 first digits of the ESP mac (#1331)

so as to don't disclose the password used for WM.
Also change the wm password from MAc to be the last 8 digits, as these will change more than the first 8 ones.
Also make consistent the ifndef qnd the parsing between WM_PWD_FROM_MAC and USE_MAC_AS_GATEWAY_NAME

platformio.ini

@@ -292,7 +292,7 @@ build_flags =
   '-DZgatewayWeatherStation="WeatherStation"'
   '-DsimplePublishing=true'
   '-DWM_PWD_FROM_MAC=true'
-  '-DGateway_Name="OpenMQTTGateway_ESP32_ALL"'
+  '-DUSE_MAC_AS_GATEWAY_NAME=true'
 
 [env:esp32dev-rf]
 platform = ${com.esp32_platform}