Handle ECH H2C query correctly

[Fangliding]

close #6259

[j2rong4cn]

内置dns的DOH h2c是支持"fromMitm"，ECH的就不能吗 613c63b

Xray-core/app/dns/nameserver_doh.go

Lines 40 to 68 in fdb9b61

	func NewDoHNameServer(url *url.URL, dispatcher routing.Dispatcher, h2c bool, disableCache bool, serveStale bool, serveExpiredTTL uint32, clientIP net.IP) *DoHNameServer {
	url.Scheme = "https"
	mode := "DOH"
	if dispatcher == nil {
	mode = "DOHL"
	}
	errors.LogInfo(context.Background(), "DNS: created ", mode, " client for ", url.String(), ", with h2c ", h2c)
	s := &DoHNameServer{
	cacheController: NewCacheController(mode+"//"+url.Host, disableCache, serveStale, serveExpiredTTL),
	dohURL: url.String(),
	clientIP: clientIP,
	}
	s.httpClient = &http.Client{
	Transport: &http2.Transport{
	IdleConnTimeout: net.ConnIdleTimeout,
	ReadIdleTimeout: net.ChromeH2KeepAlivePeriod,
	DialTLSContext: func(ctx context.Context, network, addr string, cfg *tls.Config) (net.Conn, error) {
	dest, err := net.ParseDestination(network + ":" + addr)
	if err != nil {
	return nil, err
	}
	var conn net.Conn
	if dispatcher != nil {
	dnsCtx := toDnsContext(ctx, s.dohURL)
	if h2c {
	dnsCtx = session.ContextWithMitmAlpn11(dnsCtx, false) // for insurance
	dnsCtx = session.ContextWithMitmServerName(dnsCtx, url.Hostname())
	}
	link, err := dispatcher.Dispatch(dnsCtx, dest)

[Fangliding]

不知道内置DNS是什么时候加的 我认为这不是很有必要 而且这也不是 "mitm"