[Client] DNS should have option to use IPv6 (AAAA) records

[clue]

The Connector (and underlying DnsConnector) is currently hard-coded to only look up IPv4 (A) records from the DNS server. There is currently no way to tell it to look up IPv6 (AAAA) records.

(Note that explicitly connecting to IPv4 and IPv6 addresses works just fine)

We should implement a way to explicitly define the lookup mode and eventually find a way to automatically use the correct mode (figure out if this system prefers or even supports IPv6).

Opening this ticket as a reminder and to spark the discussion - the implementation likely depends on reactphp/dns#43

[clue]

Once the underlying DNS resolver supports IPv6 (AAAA) queries, we will very likely implement an happy eyeballs algorithm here: https://tools.ietf.org/html/rfc8305 supersedes https://tools.ietf.org/html/rfc6555

I'm not working on this at the moment, but figured it's worth posting this here anyway. In case anybody feels like picking this up, PRs would be much appreciated 👍

[clue]

Resolved via #196 and #224