Add job to release CNG images to gitlab.com registry from dev registry

Towards https://gitlab.com/charts/gitlab/issues/942

What the rake task do:

1. Get list of components from pipeline in Dev registry - We can avoid this if we decide to maintain a list of components in charts, somewhere.
2. Get images from Dev registry of all those components
3. Tag and push to Com registry

Required env variables in https://dev.gitlab.org/gitlab/charts/gitlab

1. FETCH_DEV_ARTIFACTS_PAT - An access token that can use API against https://dev.gitlab.org/gitlab/charts/components/images project (in .dev) (To get list of components and for docker login)
2. PUSH_IMAGES_PAT - An access token that can use API against https://gitlab.com/gitlab-org/build/CNG (for docker login)
3. COM_CHARTS_TRIGGER_TOKEN - An access token that can trigger a pipeline in https://gitlab.com/charts/charts.gitlab.io project (in .com)