Support cancelling MultiplayerService session joining functions

Is your feature request related to a problem? Please describe.
It takes several seconds to join a session through MultiplayerService. I'd like to let users cancel a connection attempt during the connection process.

Describe the solution you'd like
I'd like to pass cancellation tokens to functions like MultiplayerService.Instance.CreateOrJoinSessionAsync.

Describe alternatives you've considered
I've tried preventing the NetworkManager from connecting to a session if my own connection function wrapping MultiplayerService.Instance.CreateOrJoinSessionAsync is cancelled, but I cannot find a clean way to do this. I have also considered modifying the Unity.Services.Multiplayer package myself, but I would rather not do this.

Non vengono indicati file o test. Inizia tracciando MultiplayerService.Instance.CreateOrJoinSessionAsync e il flusso di connessione di NetworkManager per capire dove dovrebbe essere propagato un token di cancellazione. Il lavoro è completato quando gli utenti possono annullare l’ingresso a una sessione in corso tramite le funzioni di MultiplayerService senza dover modificare personalmente il package.