Stand up Bacula system

Based on https://gitlab.com/gitlab-com/infrastructure/issues/1126#note_23997952 and https://gitlab.com/gitlab-com/infrastructure/issues/1126#note_24008091, we need to begin building a bacula cluster.

The Bacula cluster needs the following servers and services:

• Director service (controls all backup jobs and is what tells all the other pieces what to do)
• PostgreSQL service (stores backup job catalogue and other metadata)
• Storage service (controls writing the backup data to volumes)

@northrup I'm not able to find any information on recommended server specs for this. The system requirements on their site only lists applications that need to be installed. Do you have any recommendation on hardware specs for these systems?

cc/ @gl-infra