[SERIAL] Enable SERIAL to X communication (#2068)

Add Serial as a communication layer so as to transmit data to/from serial
Enable discovery of BT sensors through serial
Add serial heartbeat

Change discovery principle for interval and intervalacts, keep them always discovered and deactivate adaptivescan when changed. Instead of removing their discovery when adaptive scan is activated

Increase JSON_MSG_BUFFER_MAX as we are now using const char* and it requires more memory for Arduino Json Deserialization

Co-authored-by: Florian <1technophile@users.noreply.github.com>

main/config_LM75.h

@@ -39,7 +39,7 @@
 #define config_LM75_h
 
 extern void setupLM75();
-extern void LM75toMQTT();
+extern void LM75toX();
 
 #define lm75_always            true // if false when the current value of the parameter is the same as previous one don't send it by MQTT
 #define TimeBetweenReadinglm75 30000