feat: Add multi-project support
What
This MR adds multi-project support to the exporter.
Why
When you wish to monitor the quotas for many different projects, it could be cumbersome to run an exporter for each one. At GitLab, this will allow us to monitor all of the quotas across the many Gitaly projects with a single exporter, instead of running 15+ instances. We do not have gitaly project quotas in Thanos/mimir today.
Edited by Matt Miller