feat: add tcp_user_timeout

```json
{"streamSettings":{"sockopt": {"tcpUserTimeout": 10000}}}
```

run `gofmt -w -s .` as well

common/xudp/xudp_test.go

@@ -11,7 +11,7 @@ import (
 func TestXudpReadWrite(t *testing.T) {
 	addr, _ := net.ParseDestination("tcp:127.0.0.1:1345")
 	mb := make(buf.MultiBuffer, 0, 16)
-	m := buf.MultiBufferContainer {
+	m := buf.MultiBufferContainer{
 		MultiBuffer: mb,
 	}
 	var arr [8]byte
@@ -33,4 +33,4 @@ func TestXudpReadWrite(t *testing.T) {
 	if dest[0].UDP.Port != 1345 {
 		t.Error("failed to parse xudp buffer")
 	}
-}
+}