Lister: Simplify production deployment for listers

As of today each lister has its own db. This is mostly irrelevant as they use one table each (except for lister-debian).

This however is a pain in the neck to deploy. In regards to db creation for example.

• Stop lister/loader-debian services
• Change this to merge all dbs into one (swh-lister)
• Grant guest user read-only access
• Unify the rights to the one user swh-lister (with write permission) - [ ] Rename swh-lister to swhlister (and figure out why connection refuses to work with swhlister as user)
• Keep swh-lister for now
• Adapt puppet manifests accordingly
  • D1518: Adapt swh-lister's base code logic to deal with merged credentials
  • Adapt credentials to target the new merged db
  • !29 (closed): Merge systemd service into 1
• Deploy changes on production and start listers
  • worker01 -> happy
  • other workers
• Start back loader-debian service
• Drop old dbs (lister-github, lister-pypi, lister-npm, lister-gitlab, lister-bitbucket)
• Update the db inventory doc

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Migrated from T1772 (view on Phabricator)