Port cgit lister to the new Lister API

The cgit lister implementation must be ported to the new swh.lister.pattern.StatelessLister API

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Migrated from T2984 (view on Phabricator)

mentioned in merge request !179 (closed)

mentioned in merge request !186 (closed)

marked this issue as related to swh-scheduler#2442 (closed)

added CGit lister Lister Sprint 2021 01 priority:Normal state:wip labels

mentioned in commit e4a590fc

mentioned in commit d62e77c1

assigned to @ardumont

removed state:wip label

closed