We started doing this for install docs in de2a2d0df, because `latest`
wasn't suitable and because I didn't know about readthedocs's `stable`
feature. The result has been that even with a checklist item, we
don't reliably update the link.
Instead, use the special `stable` version identifier on readthedocs to
link automatically to the highest version it knows about.
This commit helps reduce clutter on the navigation sidebar.
Creates new directories and moves relevant files into them.
Modifies index.rst, symlinks, and image paths accordingly.
This commit also enables expandable/collapsible navigation items,
renames files in docs/development and docs/production,
modifies /tools/test-documentation so that it overrides a theme setting,
Also updates links to other docs, file paths in the codebase that point
to developer documents, and files that should be excluded from lint tests.
Note that this commit does not update direct links to
zulip.readthedocs.io in the codebase; those will be resolved in an
upcoming follow-up commit (it'll be easier to verify all the links
once this is merged and ReadTheDocs is updated).
Fixes#5265.
Tim Abbott
Cynthia Lin
Greg Price
David Rosa Tamsen