feat: add network monitors (ICMP/TCP/HTTP/DNS) (#2266)

Co-authored-by: xiaomiku01 <xiaomiku01@outlook.com>
Co-authored-by: henrygd <hank@henrygd.me>

agent/connection_manager.go

@@ -153,6 +153,7 @@ func (c *ConnectionManager) Start(serverOptions ServerOptions) error {
 //	}
 func (c *ConnectionManager) stop() error {
 	_ = c.agent.StopServer()
+	c.agent.monitorManager.Stop()
 	c.closeWebSocket()
 	return health.CleanUp()
 }