package.debian: Re-implement debian loader within the package loader mechanism
This introduces the debian package loader.
Contrary to other package loaders, a package can have multiple artifacts (per package version).
In those terms, we had to slightly adapt the swh.loader.package.loader.PackageLoader to demonstrate this. Thus the impacts on pypi, npm, deposit modules as well.
Related #2025 (closed) Related swh-core!91 (closed) Related swh-lister!114 (closed)
Test Plan
tox
Migrated from D2135 (view on Phabricator)