Roll out Runner with direct download to all GitLab-managed builds

We just recently added support for direct downloads to the runner in: gitlab-org/gitlab-runner!2093 (merged). While we are working to get this into the official 13.0 release, we could try an early version out on our private fleet of Runners on GitLab.com.

This will allow us to test, as well as begin leveraging the cost benefits as GitLab is responsible for about half of our CI usage on GitLab.com (and the attendant cost).

Roll out plan

• Once we rollout on our private runners we should be fine with a system-wide rollout: https://gitlab.com/gitlab-com/gl-infra/infrastructure/-/issues/10197