MM-34389: Reliable websockets: First commit (#17297)

* MM-34389: Reliable websockets: First commit

This is the first commit which makes some basic changes
to get it ready for the actual implementation.

Changes include:
- A config field to conditionally enable it.
- Refactoring the WriteMessage along with setting the deadline
to a separate method.

The basic idea is that the client sends the connection_id
and sequence_number either during the handshake (via query params),
or during challenge_auth (via added parameters in the map).

If the conn_id is empty, then we create a new one and set it.
Otherwise, we get the queues from a connection manager (TBD)
and attach them to WebConn.

```release-note
NONE
```

https://mattermost.atlassian.net/browse/MM-34389

* Incorporate review comments

* Trigger CI

* removing telemetry

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

app/websocket_router.go

@@ -55,11 +55,12 @@ func (wr *WebSocketRouter) ServeWebSocket(conn *WebConn, r *model.WebSocketReque
 			conn.WebSocket.Close()
 			return
 		}
-
 		conn.SetSession(session)
 		conn.SetSessionToken(session.Token)
 		conn.UserId = session.UserId
 
+		// TODO: Same logic to reconnect queue as api4/websocket.go
+
 		wr.app.HubRegister(conn)
 
 		wr.app.Srv().Go(func() {