HTTP

backport net/http for go1.20+

export net/http from: https://github.com/golang/go/tree/a70addd3b31ccb685f48867e24c6c2b4dc364a11/src/net/http

special modify:

• add TLSConn interface and not depend on *tls.Conn type

  type TLSConn interface {
      net.Conn
      NetConn() net.Conn
      HandshakeContext(ctx context.Context) error
      ConnectionState() tls.ConnectionState
  }

• add CloseHttp2Connections interface to close all http2 underlay connections

  type CloseHttp2Connections interface {
      CloseHttp2Connections()
  }

• net/http: fix NewClientConn not fully respected the passed-in context | https://go-review.googlesource.com/c/go/+/775408
• net/http/internal/http2: support non-tls.Conn TLS conn in forceCloseConn | https://go-review.googlesource.com/c/go/+/775409
• net/http: fix Server's UnencryptedHTTP2 does not work TLS without ALPN | https://go-review.googlesource.com/c/go/+/775734
• net/http: fix Transport's UnencryptedHTTP2 does not work TLS without ALPN | https://go-review.googlesource.com/c/go/+/776240