[WIP] Move CI infrastructure to GitHub Actions

[JCGoran]

According to https://github.com/orgs/community/discussions/70492#discussioncomment-7362186, public repositories have unlimited free minutes, with a time limit for each job of about 6 hours, which should be plenty for our use-case.

TODO:

• add automatic upload step
• add MPT headers (do we need this?)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.08%. Comparing base (74dcdd5) to head (5ada0ee).
Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3321   +/-   ##
=======================================
  Coverage   67.07%   67.08%           
=======================================
  Files         571      571           
  Lines      111055   111039   -16     
=======================================
- Hits        74488    74485    -3     
+ Misses      36567    36554   -13     

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[pramodk]

@JCGoran : Just mentioning - we need to update the docs from https://nrn.readthedocs.io/en/8.2.6/install/python_wheels.html#publishing-the-wheels-on-pypi-via-azure.
Especially, having the ability to just build the release artifacts without upload has been quite helpful.

[JCGoran]

Right, there's also the matter of "Azure drop URLs" being mentioned in other repos, so we should make sure those are modified accordingly.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud