[Bug]: `ImageNameSubstitutor` cannot set compatibility

A custom ImageNameSubstitutor cannot be used to mark an image as compatible substitute for another image automatically, because all implementation I found call the compatibility assertion on their constructor argument, not on the image property from the parent class that actually applies the substitution.

I want to dynamically resolve images from a Dockerfile in the root of my project to allow Dependabot/Renovate to automatically update the images for me, and thus keep my tests up-to-date. For this I wanted to use short aliases and to set compatibility dynamically. However, this isn't possible for the reasons explained.

I'm filing this as a bug, because I believe that this isn't the intended behavior. Feel free to change this.

Start with the ImageNameSubstitutor class and inspect its implementations, then trace where the parent image property and compatibility assertion are used. Add a regression test covering a custom substitutor that marks an automatically resolved image as compatible, and confirm the test passes with the Dockerfile-based alias scenario described in the issue.