swh services: Monitor swh-worker@.service's status

We should be able to monitor our ever growing list of swh services's state [1]:

• swh-worker@swh_indexer_fossology_license.service
• swh-worker@swh_indexer_mimetype.service
• swh-worker@swh_indexer_origin_intrinsic_metadata.service
• swh-worker@swh_lister.service
• swh-worker@swh_loader_debian.service
• swh-worker@swh_loader_deposit.service
• swh-worker@swh_loader_git.service
• swh-worker@swh_loader_mercurial.service
• swh-worker@swh_loader_svn.service
• swh-worker@swh_vault_cooker.service

Ideally, we should be able to be alerted when the service is not in its right state, e.g:

• stopped but should be running

• running but should be stopped

• disabled but should be enabled

• ...

• [1] https://forge.softwareheritage.org/source/puppet-swh-site/browse/production/site-modules/profile/manifests/swh/deploy/worker/

Note:

• The need is independent from the queue consumption detection (e.g. service running but associated queue consumption cancelled).
• Those services are systemd ones

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Migrated from T1202 (view on Phabricator)