Invocation cancellation doesn't cancel the payload reading of payload writing

[bentoi]

The following hangs right now:

var hangPayload = new HangPipeReader(); // a pipe reader whose ReadAsync hangs until canceled
var timeout = new CancellationTokenSource(100);
var request = new OutgoingRequest(new ServiceAddress(Protocol.IceRpc))
    {
         Payload = handPayload;
    };

connection.InvokeAsync(hangPayload, timeout.Token);

The problem is that we no longer create a linked token source in the invoke code to send the payload (we just abort the stream if the application cancellation token is canceled...). It's related to dotnet/runtime#69675 (comment)

We need to add tests to ensure that invocation and dispatch cancellation works even when the payload reader/writer hang.

[bernardnormier]

I don't understand why we're not simply creating a linked token in InvokeAsyncCore and then pass this token to SendPayloadAsync.

[bentoi]

It's in anticipation of the weird Quic implementation where the cancellation of stream.ReadAsync triggers under the hood the sending of the STOP_SENDING frame with the DefaultStreamErrorCode error code. See dotnet/runtime#69675 (comment) and the previous comments.