Use this as a replacement for nodejs-common-grpc

[JustinBeckwith]

Right now we have a lot of common layers:

• https://github.com/googleapis/nodejs-common/
• https://github.com/googleapis/nodejs-common-grpc/
• https://github.com/googleapis/gax-nodejs/

I suspect most of what's happening in nodejs-common-grpc could just be done here. The only dependents of that library are logging, bigtable, and spanner

I'd love to pick up whatever code we need out of nodejs-common-grpc, plop it here. and slowly work towards deprecating nodejs-common-grpc.

[meredithslota]

https://github.com/googleapis/nodejs-common-grpc/ has been archived, FYI only.