The new spec uses existing EchoDuplicate service in
grpc.testing.duplicate, which refers grpc.testing.Empty,
and verifies if the plugin generates this correctly as
Grpc::Testing::Empty.

The encoding of the issuer field in this cert is now a PRINTABLESTRING
as opposed to UTF8STRING in the previous server1.pem which was causing
the Go issue.

Fixes #4086.

- provides a noop logger unless the user explicit adds a logging method
  to the GRPC namespace

- adds the code-generated health service classes to the pb along with
  a README explaining how to regenerate the generated code

- adds an implementation of the Health Checker Service along with unit
  tests and an integration test

Also:
- adds a pb folder
  : in a follow-up PR, all ruby pbs + generated code will be moved to it

Corrects some other issues

- fixes status return when calls fail by always returning the status

- resolves bidi_call client's failure to return an exception on bad
  status by swapping the wait for status to the read thread

  * this also improves the cancel_after_first_response test

Also

- adds a unit test that verifies that a bidi call will time out.