Create ROCK for torchserve-kfs

[kimwnasptd]

Kubeflow is using pytorch/torchserve-kfs image, as the KServe runtime image for serving PyTorch models
https://github.com/kserve/kserve/blob/f7de5e696e8d0e64e3ed2b2493ec64244291a5c9/install/v0.11.0/kserve-runtimes.yaml#L218

The source of this image lives in https://github.com/pytorch/serve/tree/master/kubernetes/kserve and it uses the pytorch/torchserve image as base. So in order to construct the ROCK we'll need to build the base torchserve image as well.

IIUC the base pytorch/torchserve image is defined and built in https://github.com/pytorch/serve/blob/v0.8.2/docker/Dockerfile

To summarize, our ROCK will need to

• live in a new repo, that aims to provide ROCKs for pytorch/serve repo
• Have a first layer that builds the pytorch/torchserve image
• Convert the dockerfile of https://github.com/pytorch/serve/tree/master/kubernetes/kserve on top

cc @i-chvets @SamirPS

[kimwnasptd]

Also a note regarding versioning and tagging of the upstream pytorch/torchserve-kfs image:

• The tag is deduced from the version of pytorch serving runtime, which we can see in tags of the repo
• The KServe python library version can be found in https://github.com/pytorch/serve/blob/master/kubernetes/kserve/requirements.txt#L1