The QUIC listener and the QUIC/ICMP dialers unconditionally set
tlsCfg.NextProtos = ["h3", "quic/v1"], discarding any user-specified
ALPN values from TLS options (via tls.options.alpn in config).
Clone the TLS config and only apply the default NextProtos when none are
already configured, matching the existing pattern in the MASQUE HTTP/3
dialer. This enables non-HTTP/3 QUIC use cases like SMB-over-QUIC which
requires ALPN "smb".
Fixesgo-gost/gost#872
On Windows, icmp.ListenPacket("ip4:icmp", "0.0.0.0") does not reliably
deliver ICMP packets (golang/go#38427). Add a platform-specific
ListenPacket helper that binds to a discovered interface address and
enables SIO_RCVALL via WSAIoctl for promiscuous receive.
Fixesgo-gost/x#36