Attach labels to images to help the GC
We are currently spending too much money simply by pulling again and again the same images from the registry.
One thing we could do is, instead of just cleaning the images based on their latest image, also add some labels to them to give a hint at the garbage collector which image to remove.
For example, we should likely have:
- a label that says which upstream project this image is linked to.
- this should teach the gc that a fork image can be removed, there is a high chance the upstream image will come here and stay
- a label that says "there is no point in keeping this image"
- for example, the ci-templates generated images can be cleaned up right after they are used, no one actually needs them
- a label that says "keep me forever"
- the gc process should ignore them. We can use those to prevent the gc to remove the image, for stable branch for example, when there are not so many pipelines run, but still keeping them would cost less that re-pulling them all the time