Allow for image replacement in the iso-build-image executor

[eak13]

We need the ability to override/replace the image parameter value in the the iso-build-image executor. It's currently a static value & common to all phases but needs to be a variable.
https://opendev.org/airship/airshipctl/src/branch/master/manifests/phases/executors.yaml#L252

Tasks:

1. Create the image replacement transformer
2. Add the replacement reference to phases/kustomization.yaml
3. Add the override value to the airshipctl versions catalogue

[pallavgupta]

I can look into this issue. Pls assign it to me.

[pallavgupta]

https://review.opendev.org/c/airship/airshipctl/+/795713