apply mdns discovery fixes from the latest spec

[lidel]

• fix: random dns label to avoid overflow when long peerid is used (https://github.com/libp2p/go-libp2p/pull/1222)
• check if anything else changed in https://github.com/libp2p/specs/blob/master/discovery/mdns.md

[mpetrunic]

We should:

• add support for addresses other than ipv4/ipv6 (sending and parsing)
• change the service name to _p2p._udp.local
• change peer name to be randomly generated

cc @achingbrain

[github-actions[bot]]

:tada: This issue has been resolved in version 7.0.0 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: