* Add autodoc directives to generate documentation directly from
upgrade-util repo.
* Group all upgrades-related reference documentation into one group in
the sidebar, instead of having two entries.
* Mention `upgrades` vs `migrations` directory. It has been supported
since a while but nothing was explicit in the documentation.
Original commit: 91a48bfe88closesodoo/documentation#8836
Signed-off-by: Victor Feyens (vfe) <vfe@odoo.com>
