This change implements the boilerplate RPC stub generation for CIDLC
resource providers. This includes a lot of the marshaling goo required
to bridge between the gRPC plugin interfaces and the strongly typed
resource types and supporting marshalable structures.
This completes the major tasks of implementing CIDLC (pulumi/coconut#133),
and I have most of the AWS package running locally on it. There are
undoubtedly bugs left to shake out, but no planned work items remain.