feat: move to PythonCall.jl and refactor testing

[Moelf]

• move PyCall.jl -> PythonCall.jl
• remove manual installing Python related stuff in CI, now these test-only dependencies are managed in Project.toml
• use the Pkg.jl extension system (available in 1.9+) to optionally load functions in ext/AwkwardPythonCall/ when user load PythonCall.jl
• in test, we set environment variable JULIA_CONDAPKG_BACKEND="Null" to use the same Python environment we installed manually on CI, we should document this for users
• sorry about large diff, because I moved files around to make "stub" visible from the main AwkwardArray.jl source file

[Moelf]

there must be a better way to check layout other than hard coding all these types, these type parameters shouldn't be considered fully stable

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (9f125f1) 71.32% compared to head (9c08674) 71.21%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #48      +/-   ##
==========================================
- Coverage   71.32%   71.21%   -0.11%     
==========================================
  Files           3        4       +1     
  Lines        1618     1619       +1     
==========================================
- Hits         1154     1153       -1     
- Misses        464      466       +2     

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[ianna]

Thanks, @Moelf ! BTW, why the 15 line difference if it's just a move? I used a JuliaFormatter is that the reason? Thanks!

[Moelf]

No I moved but also need to remove top and bottom lines for the module definition.

Because module definition is now in the AwkwardArray.jl main source file

[ianna]

Great! Let's merge it if you are done with it. I see what's not covered by the tests. We can add them in the next PR.