A QUICker SASE client: re-building Proxy Mode

What this post added

Re-built the Cloudflare One Client's proxy mode from the ground up, deprecating WireGuard for proxy mode in favor of QUIC. This involves leveraging MASQUE (part of QUIC) for proxying IP packets and using QUIC streams for direct L4 proxying via HTTP/3 with the CONNECT method. This architectural shift bypasses smoltcp, leverages native QUIC benefits for congestion and flow control, and allows for tuneable parameters, resulting in doubled download/upload speeds and decreased latency.