feat: implement server-initiated heartbeat in msgGateway module (#2404)

* feat: implement send ping msg when platform is web in gateway.

* add context life cycle control.

* feat: implement heartbeat logic in msggateway.

* update heartbeat logic.

* update to correct method name and comment.

* update initiate heartbeat logic.

* rename ws_server

* update writePingMsg logic

* update log level to warn.

internal/msggateway/long_conn.go

@@ -16,10 +16,11 @@ package msggateway
 
 import (
 	"encoding/json"
-	"github.com/openimsdk/tools/apiresp"
 	"net/http"
 	"time"
 
+	"github.com/openimsdk/tools/apiresp"
+
 	"github.com/gorilla/websocket"
 	"github.com/openimsdk/tools/errs"
 )