Add tests for cancellation

[smaye81]

This adds tests for cancellation logic based on the cancel_timing oneof in the test request.

[smaye81]

Would like to put these into the populateExpectedResponse methods, but want to refactor that to use JSON first so it doesn't cause the test to balloon even further and make the refactor even more difficult.

[smaye81]

As we discussed offline, this is because of the stream.Header call in the gRPC client implementation. That call blocks until header metadata is sent, but the server stream endpoint sends the header information with the first response. So, the stream.Header call blocks until a response is sent and then the context is cancelled. So right now, the expectations for responses on server streams won't work.

This can be fixed with a change on the reference server and the gRPC server:

Reference Server

• should call stream.Send(nil) after setting the headers.

gRPC Server

• should call stream.SendHeader(headerMD) (instead of SetHeader)

However, doing the above causes a "protocol error: incomplete envelope: context deadline exceeded" error to be thrown by Connect-Go on the server stream timeout tests (presumably from here).

[jhump]

Aside: FWIW, this shouldn't be necessary. The runner knows that full-duplex isn't allowed with HTTP 1.1 and won't bother applying test cases with full-duplex bidi stream type to that HTTP version.

[smaye81]

Nice. I combined bidi.yaml into basic.yaml then since we didn't need to specify HTTP versions.