Improve generated OpenAPI/Swagger documentation

Tweak our proto settings to improve the generated OpenAPI / Swagger docs:
- [ ] Loading into https://editor.swagger.io/ complains that the `info` block is missing a `version
- [ ] The proto types are prefixed with `proto`: see if we can use nicer names through an annotation?
- [ ] Fix how [title and descriptions](https://github.com/GoogleContainerTools/skaffold/blob/be6ae575ff327b751df38ba798183028bdc76375/hack/proto/Dockerfile#L78-L81) are being set, or report upstream

See the [grpc-gateway docs](https://grpc-ecosystem.github.io/grpc-gateway/docs/mapping/customizing_openapi_output/).