Consolidate cos7 and alma8 docker files

[isuruf]

Checklist

• Used a personal fork of the feedstock to propose changes
• Bumped the build number (if the version is unchanged)
• Reset the build number to 0 (if the version changed)
• Re-rendered with the latest conda-smithy (Use the phrase @conda-forge-admin, please rerender in a comment in this PR for automated rerendering)
• Ensured the license file is being packaged.

[isuruf]

@conda-forge/core, this is ready

[jakirkham]

When it comes to distributions, think it is better to keep them in separate Dockerfiles

For example this is now adding CentOS 7 repos to Alma, which don't make sense there. Plus the naming of the directories is confusing

If the goal is simply to consolidate more content, would suggest taking the yum step changed here and moving it into a script that all images call

[isuruf]

For example this is now adding CentOS 7 repos to Alma, which don't make sense there. Plus the naming of the directories is confusing

We are not. The fix_rpm uses those repos only for centos7. We would have to add alma8 repos there in the future as well.

This PR reduces code duplication and the only thing that this PR does more is to copy centos7 repos and delete them without using them in alma8 which is okay IMO.

[isuruf]

Also, it looks like there's a single Dockerfile for centos7 and ubi8 cuda images. Those are two different distributions, yet we use one Dockerfile

[h-vetinari]

I like the deduplication. Also, both images are RHEL-derivatives, so a lot is the same, and the differences are small enough that unification is beneficial IMO.

[isuruf]

@jakirkham let me know if there are any other objections.

[h-vetinari]

As a great illustration why this PR is beneficial, the addition of alma9-based images becomes absolutely trivial.