Also drop the SWH prefix as this is redundant.

swh.lister.gitlab: make the 'instance' a constructor parameter

Related T989

And remove uneeded indexing name from the RangeListerTask

Related T989

Related T989

Samples:
- https://0xacab.org/api/v4/projects/
- https://framagit.org/api/v4/projects/
- https://salsa.debian.org/api/v4/projects/
- https://gitlab.com/api/v4/projects/
- https://gitlab.freedesktop.org/api/v4/projects/
- https://gitlab.gnome.org/api/v4/projects/
- https://gitlab.inria.fr/api/v4/projects/

Related T989

Multiple issues wish for the api to converge on 429 but nothing is
clear nor documented yet:
- https://gitlab.com/gitlab-com/infrastructure/issues/348
- https://gitlab.com/gitlab-org/gitlab-ce/issues/41309
- https://gitlab.com/gitlab-org/gitlab-ce/issues/46522

The only response code mentioned in the documentation is
403 (https://docs.gitlab.com/ee/api/README.html#status-codes).

Related T989

Related T989

Related T989

Related T989

This impacts:
- the credentials reading which needs to be indexed per instance
- the models since a new instance column needs to referenced and
  indexed

Related T989

Related T989

And not 'project' id

Related T989

This is now running through the swh scheduler

Related T989

originally appeared on the Software Heritage blog at
https://www.softwareheritage.org/2017/03/24/list-the-content-of-your-favorite-forge-in-just-a-few-steps/
by Avi Kelman

Closes T762