Add repository rst files in the sphinx docs

[farhan]

Ticket: https://github.com/openedx/edx-platform/issues/33950 Planning ticket: https://github.com/openedx/edx-platform/issues/33047

Details of Implementation:

repository_docs.py contains the code to:

1. Fetch the list of all the .rst docs/files in the repository
2. Copy all these .rst files into docs directory to make them linkable in the sphinx build process.
3. Generate the index.rst files in the new created directories to link all the copied .rst files in the sphinx docs.

I have closed following PR's and terminated these previous implementations associated with this feature as these approaches have technical limitations to proceed. For example to refer the .rst files outside of root docs directory as discussed here https://github.com/openedx/edx-platform/pull/33997 https://github.com/openedx/edx-platform/pull/34405

Testing instructions

1. Checkout the branch
2. In lms-shell go to /edx-platform/docs
3. Run make html command to generate docs
4. Explore docs directory for the files generated in the build process
5. Open docs/_build/html/index.html in browser to navigate the docs
6. Docs will be listed on path edx-platform/docs/_build/html/references/docs/index.html

Screenshots