scheduler.cli.journal: Add `swh scheduler journal visit-stats` cli
This adds the cli entrypoint to actually process origin_visit_status topic (which writes to the origin_visit_stats db table).
Note that:
- the cli name
visit-stats
could be changed if someone has a better name in mind - this does not open the swh.journal as optional dependency for the scheduler which may be a tad cumbersome
Related to #2967 (closed) Depends on !176 (closed)
Migrated from D4876 (view on Phabricator)