add `preflight` check to GH actions for docker-images

[razvan]

OpenShift Preflight is a tool to check if container images are valid for OpenShift.

#337 also features the preflight check, have a look to see how to run it for ZK. The binary can be downloaded from GitHub

Acceptance Criteria

• the docker-images and operator-templating repository have a github action that runs preflight to check if a container image is valid.
• The image is checked before it is pushed. Difficult to do because the preflight can only check already published images
• The check is required for PRs to merge. Difficult to do with our current structure in the CI. But it's fine, the preflight check is quite basic.

Steps

• add a GH action as a test to one repo (maybe ZK)
• if if works, add it to operator templating
• Also add it to docker-images: Feat/preflight check docker-images#334 Refactor image building and add preflight checks. docker-images#339

[fhennig]

It looks like preflight doesn't support checking containers locally, so we'll have to push them, and check afterwards. This kind of makes the check optional anways.

I've made an upstream ticket: redhat-openshift-ecosystem/openshift-preflight#896

Edit: Doesn't work.

The docs mention a way to run a local registry and check in there

[fhennig]

Update:

• I've tested it in ZK and it worked, it is now rolled out to all operators
• I'm working on the PR for docker-images, I got a first minimal version working there as well

[fhennig]

Razvan made a PR that's much cleaner than what I hacked together: stackabletech/docker-images#339