Addons: always sort versions in descending order (#11691)
* Addons: always sort versions in descending order
We were mixing ascending and descending when listing the versions,
we now always sort in descending order. Even if the version
fails to parse, we still sort it in descending order as fallback.
Closes https://github.com/readthedocs/readthedocs.org/issues/11689
* Fix tests