net: mdns_responder: Implement probing support

The mDNS probing is described in RFC 6762 chapter 8.1.
The code will send an unsolicited mDNS query to network and
will check if there are existing hosts with the same name.
If there are, then the mDNS responder will not respond to
queries it is configured to use.

Fixes #84333

Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no>