Add a new manual action which will run QA tests for CE/EE merge requests
After all steps described in #29 (closed), #30 (closed) and #31 (closed) are done, we should add a new manual job in CE/EE MRs which will:
- fetch GitLab Omnibus
- build image using a GitLab code that pipeline is running for
- build image with instance tests
- clone GitLab QA standalone tool
- execute QA tests
With this approach we do not need to push Docker images to the registry which should save a lot of resources. Later, we can easily refine this strategy.