IPv6 Support

[Prolu7]

Is your feature request related to a problem? Please describe.
A lot of ISPs (especially in Europe) including mine, only support DS-Lite, which means we only have an IPv6 address and a natted IPv4 address. This means connecting to IPv4 can sometimes be very slow and you cannot host IPv4-only servers.

Describe the solution you'd like
Please add IPv6 support, so the connection uses the preferred method like described in RFC 8305, the Happy Eyeballs (Fast Fallback) algorithm.

Describe alternatives you've considered
I've considered buying a 3rd party server and ISPs. Both don't fix the slow IPv4 problem.

Additional context
Happy Eyeballs Alogrithm
IPv6 Adoption

[Starystars67]

I've moved this issue to the Launcher repo from the Server repo due to the Server already supporting IPv6.
The Launcher however does not support IPv6 presently so here feels more appropriate.