[Feature Request] Expose client health check

[cretz]

Is your feature request related to a problem? Please describe.

Need to be able to make health check call on client.

Describe the solution you'd like

Easiest way may just be to expose the entire https://github.com/grpc/grpc/blob/master/src/proto/grpc/health/v1/health.proto that the server implements in the same way we expose workflow service and operator service. I can build the request and make the call as needed.