Client & CLI updates

[thedodd]

Finish updating the client library and CLI to work with the updated networking model. Depends upon:

• [x] #63 for the availability of a Stream/StatefulSet's K8s Service to be provisioned for a stable network address for the metadata streams,
• [x] #59 for implementing the server side metadata stream interface.
• [ ] update client code to use new gRPC interface.
• [ ] implement client side LB pattern.
  • should we allow for publishing to a specific partition (hashing and such)?
  • or should we enforce the pattern that all partitions should be considered equal, and we use opaque LB strategy?