Public Grafana instance

There is some metrics which it make sense to make public, ex:

• https://monitoring.archlinux.org/d/x5L3ZBJMk/arch-linux-archive?orgId=1
• https://monitoring.archlinux.org/d/PKkRg-FGz/rebuilderd?orgId=1

Steps:

1. Create a new organization for the public dashboards and datasources
2. Enable anonymous authentication
3. Setup a secondary Prometheus instance and add it to the organization
4. Use Prometheus remote write to ship selected metrics to the secondary Prometheus instance
5. Add dashboards to the organization