Add proxmox / ceph monitoring

The ceph and proxmox clusters is not really monitored actually. (Ceph storage is used by the proxmox cluster in the current configuration to store the vm disks.)

We should add some probes to raise alert on icinga in case of wrong behaviors for both stack:

• ceph [1]
• proxmox [2]

And if possible track some metrics on prometheus/grafana.

• [1] https://docs.ceph.com/en/nautilus/mgr/prometheus/

• [2] https://blog.zwindler.fr/2020/01/06/proxmox-ve-prometheus/

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Migrated from T3462 (view on Phabricator)