Reusable matrix entries

[altendky]

Draft for:

• Make it actually work
• Formalize the script (a separate project?)
• A test to verify the generated workflow is up to date
• Retarget to main branch after Freeze with PyInstaller #30 is merged
• Dedupe the names as well...

[codecov]

Codecov Report

Merging #34 (6cccc21) into main (ab991de) will not change coverage.
The diff coverage is n/a.

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  Lines          595       595           
  Branches        43        43           
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  Hits           595       595           

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[altendky]

So after spending a few hours figuring out 7b8eeb3, I gave in and concluded that _something_ needed to be different. This repetition of the matrix entries is just crazy (this isn't the only repository I deal with it in...). My first attempt was to do some silly matrix games and generate output from one job and reference in the next and.... *ugh* I've already done this (because it was really needed) in https://github.com/altendky/romp in Azure Pipelines but I couldn't quite get it to work here. Used this page for a bit of reference.

So the underlying problem is GitHub Actions hasn't gotten around to YAML anchors.
https://github.community/t/support-for-yaml-anchors/16128

Anyways, the present implementation here involves just writing a workflow with anchors and then running it through some python/pyyaml to resolve and duplicate the anchors to make GitHub Actions happy.