QUIC proxy works like kcp proxy, it can proxy TCP streams and transfer data with QUIC.
QUIC has better congestion algorithm (BBR) for network with both high loss rate and high bandwidth.
QUIC proxy can be enabled by passing `--enable-quic-proxy` to easytier in the client side. The proxy status can be viewed by `easytier-cli proxy`.
icmp/udp proxy do not rely on kernel net stack, but currently not handle ip fragmentation correctly.
this patch add ip resembler to merge fragmented ip packet for udp/icmp proxy