Refactor WrapLink logic (#5288)

https://github.com/XTLS/Xray-core/pull/5133
https://github.com/XTLS/Xray-core/pull/5286

common/mux/server.go

@@ -5,7 +5,6 @@ import (
 	"io"
 	"time"
 
-	"github.com/xtls/xray-core/app/dispatcher"
 	"github.com/xtls/xray-core/common"
 	"github.com/xtls/xray-core/common/buf"
 	"github.com/xtls/xray-core/common/errors"
@@ -64,7 +63,9 @@ func (s *Server) DispatchLink(ctx context.Context, dest net.Destination, link *t
 	if dest.Address != muxCoolAddress {
 		return s.dispatcher.DispatchLink(ctx, dest, link)
 	}
-	link = s.dispatcher.(*dispatcher.DefaultDispatcher).WrapLink(ctx, link)
+	if d, ok := s.dispatcher.(routing.WrapLinkDispatcher); ok {
+		link = d.WrapLink(ctx, link)
+	}
 	worker, err := NewServerWorker(ctx, s.dispatcher, link)
 	if err != nil {
 		return err