move symlinks to python, in line with other runtime repos

[rahult-graphcore]

This PR duplicates what was done in the other 3 runtimes, to move the symlinking code to a json config and python script, to make it more easily extendable and manageable. Pytorch runtime reference PR: https://github.com/gradient-ai/Graphcore-Pytorch/pull/52/files

Testing done:
Use diff and tree to compare the sorted tree structure of the tmp directory for a Paperspace notebook started using the main branch vs this feature branch, and verify they are identical. Steps:

1. Created 2 notebooks on paperspace, one on main branch, one on this feature branch. For each notebook, after setup.sh etc. finished executing, start a terminal, then
2. apt-get update -y && apt-get -y install tree
3. cd /tmp
4. tree -afi > /notebooks/<branchname>.tree
5. Download the 2 .tree files to local machine, then do diff main.tree feature.tree and verify there's no difference between the two.

[payoto]

LGTM

[payoto]

Thanks for the detail of how you tested 👌