Berry add module mdns

[s-hadinger]

Description:

Requires #define USE_DISCOVERY

Add Berry support for mdns announces (preparation for future Matter support):

• Added import mdns
• mdns.start([hostname: string]) -> nil: start or restart mdns, specify hostname or use tasmota.hostname() if none provided (default)
• msdn.stop() -> nil: free all mdns resources
• mdsn.set_hostname(hostname:string) -> nil: change the hostname
• mdns.add_service(service:string, proto:string, port:int, txt:map) -> nil: add a service declaration using the current hostname as instance name, and specify TXT fields as a map
• Added tasmota.hostname() -> string: return the hostname
• Added Berry low-level functions be_ismapinstance() and be_islistinstance()

Example of declaration as Matter device:

import mdns
mdns.start()
mdns.add_service("_matterc","_udp", 5540, {"VP":"65521+32768", "SII":5000, "SAI":300, "T":1, "D":3840, "CM":1, "PH":33, "PI":""})

Checklist:

• The pull request is done against the latest development branch
• Only relevant files were touched
• Only one feature/fix was added per PR and the code change compiles without warnings
• The code change is tested and works with Tasmota core ESP8266 V.2.7.4.9
• The code change is tested and works with Tasmota core ESP32 V.2.0.5
• I accept the CLA.

NOTE: The code change must pass CI tests. Your PR cannot be merged unless tests pass