After a first attempt with D7812 this one use a different strategy to
retrieve origins.

Fetch and extract "core.files.tar.gz", "extra.files.tar.gz" and "community.files.tar.gz" from archives.archlinux.org. That step ensure that we have a list of "official" packages.
Parse metadata from 'desc' file to build origins url.
Scrap the origin url to get artifacts metadata that list all versions of a package.

It also fetch and extract unofficial 'arm' packages from archlinuxarm.org but in this case we can not get all versions of an arm package.

Related T4233