Add an option to create arch specific, python version independent pkgs

[isuruf]

Description

Checklist - did you ...

• Add a file to the news directory (using the template) for the next release's release notes?
• Add / update necessary tests?
• Add / update outdated documentation?

Implementation for ABI3 as described in https://github.com/conda/ceps/blob/main/cep-0020.md
This implementation depends on a specific python-abi3 package (already in conda-forge at https://github.com/conda-forge/python-abi3-feedstock) in host to set the correct runtime dependencies.
By being ABI3 agnostic, we leave room for other standards like ABI4, HPy to be supported.
Added documentation has an example, and a more complicated example for conda-forge is at https://github.com/conda-forge/python-abi3-feedstock/blob/main/recipe/example-meta.yaml

[codspeed-hq]

CodSpeed Performance Report

Merging #5456 will not alter performance

_{Comparing isuruf:python-ver-indep (1729889) with main (caa6d2f)}

Summary

✅ 5 untouched benchmarks

[beckermr]

Is there a test here that asserts that the output package is put into an arch-specific part of the repodata (e.g., linux-64)? It is not obvious to me from the changes that this would happen, but I am still a conda-build n00b.

[jaimergp]

Thanks for the docs! We are missing the news/ entry and perhaps a short description in the PR linking to the relevant issues, discussions, CEPs, etc. I'll review once those are in.

[isuruf]

Thanks. Added a news entry and updated the PR description.

[wolfv]

Awesome work!

[jezdez]

Suggested change

	in [CEP20](https://github.com/conda/ceps/blob/main/cep-0020.md).
	in [CEP 20](https://github.com/conda/ceps/blob/main/cep-0020.md).