Introduce a simpler base pattern for lister implementations.

This new pattern uses the lister support features introduced in swh.scheduler to replace the database management done in previous iterations of the listers.

Depends on !141 (closed). Requires swh-scheduler!146 (closed) from swh.scheduler (for tests).

Test Plan

new tox tests introduced

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Migrated from D3425 (view on Phabricator)