Finalmask: Add XDNS (relies mKCP, like DNSTT), header-*, mkcp-* (#5560)

And https://github.com/XTLS/Xray-core/pull/5560#issuecomment-3825430761

transport/internet/kcp/connection_test.go

@@ -16,9 +16,7 @@ func (NoOpCloser) Close() error {
 }
 
 func TestConnectionReadTimeout(t *testing.T) {
-	conn := NewConnection(ConnMetadata{Conversation: 1}, &KCPPacketWriter{
-		Writer: buf.DiscardBytes,
-	}, NoOpCloser(0), &Config{})
+	conn := NewConnection(ConnMetadata{Conversation: 1}, buf.DiscardBytes, NoOpCloser(0), &Config{})
 	conn.SetReadDeadline(time.Now().Add(time.Second))
 
 	b := make([]byte, 1024)