Evenly distribute GitLab-CE/EE tests
This allows us to automatically distribute test for ruby apps: https://github.com/ArturT/knapsack/issues/34 with minimal (or for now) no changes to the coordinator. Not sure if there are so intelligent solutions for other languages, but support for multiple concurrent nodes is quite common.
This boring solution, not really very innovative, but it does not require any changes on our side other then updating our .gitlab-ci.yml and possibly in the future making it easier to have multiple builds for a job.
We can use current: caching and artifacts passing to automatically update the knapsack report with timings of a tests.