Migrate the staging database server to bullseye

Dedicated task for the staging upgrade Plan: -stop the loaders and listers workers -stop the indexers -stop the scheduler runners * -on db1: - connect to the serial console => swh-ceph-osd1-adm.inria.fr pass in the credential store (infra/db1.staging/idrac) - disable puppet - stop and disable postgresql - perform the last buster upgrade - reboot - perform the bullseye upgrade - reboot - restart and enable postgresql - restart puppet -restart the scheduler runners -restart the indexers -restart the lister / loaders

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Migrated from T3813 (view on Phabricator)