Add python wheel staging to GitHub Actions build_release_candidate

[kennknowles]

This directly ports the logic in build_release_candidate.sh to the GitHub Action in `build_release_candidate.yml

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[codecov]

Codecov Report

Merging #28822 (57821c1) into master (b9398e0) will not change coverage.
Report is 2 commits behind head on master.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #28822   +/-   ##
=======================================
  Coverage   72.21%   72.21%           
=======================================
  Files         684      684           
  Lines      101235   101235           
=======================================
  Hits        73104    73104           
  Misses      26556    26556           
  Partials     1575     1575           

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[damccorm]

We still need to se the GITHUB_TOKEN here as an env var (it won't be automatically visible).

So GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

[damccorm]

I'd also still prefer we pass the env location into the script to be explicit.

[kennknowles]

Done & done

[damccorm]

We need to add STAGE_PYTHON_SOURCE as an input at the top of the file.

[kennknowles]

Done (changed also to ARTIFACTS since it is more than source I think.

[damccorm]

signing_key is not assigned, you can include it as an env var using ${{steps.import_gpg.outputs.name}} like we do above.

Also note that local-user here is actually the name of the key, not the key itself

[kennknowles]

Done

[damccorm]

Thanks!