update client stream to receive and return server response

[asutula]

It is typical for grpc client streams to receive a final response from the server after ending the client stream. This wasn't implemented in ts-protoc-gen as described and exemplified in https://github.com/improbable-eng/ts-protoc-gen/issues/105. This PR fixes that.

Changes

• Updated code generation for client stream (RequestStreams) onEnd callbacks to take an additional resp: ResT | undefined parameter to which the server response can be passed.
• Updated generated grpc client code to get the server response and pass it to the onEnd listeners.
• Updated the generated Typescript definitions to reflect all this
• Generated example/test code in the repo so it reflects these changes
• Added a test to test these changes

Verification

Added a test in the client streaming tests that specifies the mock grpc transport return a message, and verifies that message was received.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.