Manage private project repos through sync

In line with eclipsefdn/helpdesk#1716 (closed) we need to add a way of managing private repos as they will be enabled in the near future. The goal with this functionality is to use the data from the projects API for Gitlab and to look for projects outside of allowlisted areas (eclipse, eclipse-ig, eclipse-wg, eclipsefdn, and security come to mind as root groups to ignore), check their last active date, and schedule deletion if they have not been active for at least 90 days.

In project returns, there should be a few fields that will be critical to this work, including last_activity_at, and visibility. We don't want to delete projects that are public as they are typically forks for projects. We may want to clean them up in the future, but not with this iteration of the work.

@mbarbero are there any other exceptions where we don't want to delete private projects?