Script to merge container image lists of each deployment (capo, capm3, etc.)

What does this MR do and why?

This MR adds a script to merge multiple images_ref JSON files into one unified list, featuring the mapping between images and units. This script should be triggered when a release is tagged (manually or in CI) and may aid in security scanning and air-gapped deployments.

Related reference(s)

!3161 (merged)

Test coverage

I manually created multiple images_ref reports and used the script to successfully merge them.

Please, review the script and its output format. 🙏

Here are some input and output files: image_refs.zip. To test the execution of the script, run the following command: python merge_image_refs.py -i image_refs_* -o output.json