too much stuff in there:
- Explicit the actual task-type needed for each listers (in a dedicated conftest per lister)
- Clarify fixtures (drop indirections, reuse fixtures)
- Unbreak the debian lister test (due to shared state between state which is now resetted) [1]
In the end, the reuse of the swh.core.db.db_utils postgresql_fact did not occur yet ¯\_(ツ)_/¯
[1] https://jenkins.softwareheritage.org/job/DLS/job/tests/1043/console