feat(server): add IPv6 support for server and client compatibility

[Knogle]

Ahoy, hope you guys are doing fine.

This PR brings the server-side pieces needed for IPv6 support in our current launcher/client compatibility setup.

• IPv6-aware handling in the launcher-facing probe/query path.
• Connect probe improvements for IPv6 endpoints (including handshake/cookie flow handling).
• Server-side updates aligned with the launcher IPv6 bridge strategy, so legacy client constraints can still connect through the compatibility path.

The launcher can already resolve/query IPv6, but end-to-end connect needs both sides aligned.
This PR provides the server-side support required so the new launcher IPv6 workflow can complete real joins reliably.

• IPv6 probes and connect flow are now working together with the launcher changes.
• Establishes a usable baseline for IPv6 servers while preserving compatibility with legacy SA:MP client behavior.

Notes

• This is a preliminary but functional step focused on practical connectivity.
• Further hardening/cleanup can be done incrementally in follow-up PRs once broader testing is complete.

I've got the .pcap attached for external traffic and loopback if anyone wants to go through it.

Also see
openmultiplayer/RakNet#31
openmultiplayer/launcher#387

loopback.zip
ipv6proxyfiltered.zip