pagure: Implement lister for pagure forges
Pagure is a git-centered forge, python based using pygit2.
Its REST API enables to easily list all projects hosted in an instance so the lister implementation is quite simple.
Related to swh/meta#5043 (closed).
It seems urgent to have it based on my understanding and it was quite simple to implement so here it is.
$ swh lister run -l pagure url=https://src.fedoraproject.org
ListerStats(pages=581, origins=57959)