Operator to remove image duplicates before scheduling a scan job

[kchestnov]

Current behavior of operator is to read target pod specs and for each container inside the pod a new container is created to scan target container image.

Consider the following situation:

• Target pod has multiple containers sharing similar images , e.g. cilium
• Operator creates a pod with 10 containers each of them runs the same command and creates same report.
• There is an option to overcome this situation in case of initContainers, but in a more generic case it would be nice to use a set instead of list of images

This behavior, combined with #2267 might explode resources required to scan a pod, e.g. by setting requests 200M and limits 2G (to include all possibilities of images in a cluster) you'll schedule a pod with 2G request and 20G limit which might OOM the whole node.