Auto generate `occ` namespace overviews

[joshtrichards]

We should auto-generate the occ the command overview sections. We can use GitHub workflows to run occ periodically against new Nc releases.

This should greatly improve the accuracy of the Admin Manual occ chapter and streamline the labor intensity of keeping it up-to-date.

feature: occ

[joshtrichards]

This Sphinx extension could facilitate this:

https://github.com/OpenNTI/sphinxcontrib-programoutput