Right now in gRPC, every call to end() will result in the termination status being set to CallbackCanceled. However, to enable better diagnostics and metrics of stream's status, it would be better to call asyncFinish() and then update the termination status based on that rather than just cancelling.

We could add a new function to the Session API, named something like asyncEnd, that gracefully finishes a session and allows us to have better visibility into the termination status of streams.