[TODO] Rewrite the plugin fetcher as a Sphinx extension

[webknjaz]

Hey @nicoddemus @bluetech @RonnyPfannschmidt @The-Compiler are y'all married to the idea of committing this table to the Git repo as RST? I know how to write an in-repo Sphinx extension that would do this on build with proper caching. This would eliminate the need to keep updating RST.

Originally posted by @webknjaz in #12607 (comment)

[webknjaz]

I lost track of this and Bruno's endorsement of the idea (#12607 (comment)). So I'm filing this issue for visibility.

[webknjaz]

This will need a new directive like https://github.com/ansible/ansible-lint/blob/a85f191/docs/rules_table_generator_ext.py#L38-L76. And some cache processing, perhaps: https://github.com/sphinx-contrib/sphinxcontrib-towncrier/blob/01bb987/src/sphinxcontrib/towncrier/ext.py#L295-L326.

[Pierre-Sassoulas]

Generally I like committing the resulting rst because it's easier to review the changes and you can see problems in the generation that you would miss otherwise. In that case the plugin list is very stable, automated, and barely need a review so +1 from me.

[RonnyPfannschmidt]

I prefer the split of generate and doc build

I don't want to make general doc building dependent on a potentially failing process