mdns: T5615: Allow controlling IP version to use for mDNS repeater

This commit adds a new configuration option to the mDNS repeater service
to allow controlling which IP version to use for mDNS repeater.

Additionally, publishing AAAA record over IPv4 and A record over IPv6 is
disabled as suggested.

See:

• https://github.com/lathiat/avahi/issues/117#issuecomment-1651475104
• https://bugzilla.redhat.com/show_bug.cgi?id=669627#c2