Overhaul build process with setuptools_scm and written version file

[djhoese]

This fixes various issues encountered with new versions of setuptools_scm. Pyspectral was depending on a deprecated package setuptools_scm_git_archive whose features are now included upstream in setuptools_scm.

Additionally I removed a hack in setup.py that was copied from satpy to tell setuptools_scm to not copy every file that git knows about. This has been worked around in recent versions of setuptools_scm by allowing you to exclude files from your MANIFEST.in. However, I find it very annoying to have to exclude everything that might be unnecessary so instead I exclude everything and then add what we want back in.

I removed all the mocking in the docs and just added those dependencies to the RTD environment.

I also switched from a dynamic version loading that was using pkg_resources to a configuration where setuptools_scm writes a pyspectral/version.py file. This is better for import performance and avoids the usage of the deprecated pkg_resources package. This package is used elsewhere in pyspectral and will need to be replaced with importlib.resources (I think that's the name) so FYI @adybbroe.

Let me know if you have any questions. We need this merged ASAP so that other packages can install pyspectral from source again.

• Closes #xxxx
• Tests added
• Tests passed: Passes pytest pyspectral
• Passes flake8 pyspectral
• Fully documented
• Add your name to AUTHORS.md if not there already

[codecov]

Codecov Report

Merging #197 (9a21305) into main (fb40e2d) will decrease coverage by 0.01%.
The diff coverage is 60.00%.

@@            Coverage Diff             @@
##             main     #197      +/-   ##
==========================================
- Coverage   89.23%   89.23%   -0.01%     
==========================================
  Files          23       23              
  Lines        2537     2536       -1     
==========================================
- Hits         2264     2263       -1     
  Misses        273      273              

Flag	Coverage Δ
unittests	89.23% <60.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
pyspectral/tests/test_rayleigh.py	100.00% <ø> (ø)
pyspectral/__init__.py	60.00% <33.33%> (-6.67%)	⬇️
pyspectral/tests/test_utils.py	98.09% <100.00%> (ø)
pyspectral/utils.py	90.98% <100.00%> (ø)

[mraspaud]

Looks good to me, just small questions.

[djhoese]

pre-commit.ci autofix