Add go-tfdata integration (tests)

[knopt]

There where 4 problems:

• go-tfdata is private
• go-tfdata is on gitlab-master.nvidia.com, not github.com/NVIDIA/go-tfdata
• go-tfdata is on gitlab-master.nvidia.com, but declares itself as github.com/NVIDIA/go-tfdata
• go mod tidy doesn't look at build dependencies

See README.md for steps on how to make it work.

Additionally, integration could be slightly easier if we decided on a common interface/type of Sample. I believe Bytes is not the best choice from go-tfdata perspective

[knopt]

git config --global url."ssh://[email protected]:12051/".insteadOf "https://github.com/NVIDIA/go-tfdata"

might be even better, and then no replace in go.mod. I'll try to change it.