Support for Jaeger gRPC trace emitter

[RashmiRam]

We have a setup where jaeger collector listens for traces and send it to our backend servers and we want to do the load test on whole flow of jaeger collector + our backend servers.

If you think this is a value add to the load-generator, I would be happy to send a PR for the same.

[pjanotti]

Hi @RashmiRam - this is a good addition to the load generator, it will be welcome.