Hysteria transport: Add congestion config (""/"reno"/"bbr"/"brutal"/"force-brutal") (#5549)

Closes https://github.com/XTLS/Xray-core/issues/5546

proxy/hysteria/ctx/ctx.go

@@ -0,0 +1,20 @@
+package ctx
+
+import (
+	"context"
+)
+
+type key int
+
+const (
+	requireDatagram key = iota
+)
+
+func ContextWithRequireDatagram(ctx context.Context) context.Context {
+	return context.WithValue(ctx, requireDatagram, struct{}{})
+}
+
+func RequireDatagramFromContext(ctx context.Context) bool {
+	_, ok := ctx.Value(requireDatagram).(struct{})
+	return ok
+}