Right now, we have a helper function that ASSERTs if a client stub can connect with the gRPC server. However, when that assertion fails like in [BF-30671] title|https://jira.mongodb.org/browse/BF-30671], the line number of the failure is not useful because it is just the line number of the assert inside the function call. Change this helper to be a macro so that we get useful line number information in case of a failure.