close failed v2ray upgrade connections

[winter-loo]

Summary

• close the underlying TCP connection when a v2ray WebSocket upgrade fails after dialing
• close the underlying TCP connection when a v2ray HTTP Upgrade handshake fails after dialing
• close the HTTP Upgrade response body on unexpected upgrade status

Root cause

Both transport clients open a lower-level TCP connection before validating the upgrade handshake. Some failure paths returned without closing that connection, so repeated failed URL tests could retain socket/AFD handles on Windows even though they no longer appeared as active established TCP connections.

Validation

• Built a patched Windows binary from v1.13.13 and replaced the running sing-box process.
• Before the fix, repeated URL tests caused sing-box handles, AFD handles, and TCP Bound endpoints to grow into the thousands, eventually producing Windows 10055 / insufficient buffer space errors.
• After the fix, the process was monitored for many hours with handles staying around 540-565, AFD handles around 50-80, TCP Bound endpoints in single/double digits, and proxy/API ports remaining reachable.