Drop python 3.8 and numpy 1.20

[joshmoore]

Various PR builds (e.g. https://github.com/zarr-developers/zarr-python/actions/runs/6704243768/job/18216294128?pr=1543) are failing on Python 3.8. According to https://scientific-python.org/specs/spec-0000/ dropping Python 3.9 is suggested by the end of this year. As a step in that direction, this PR drops 3.8 and adds 3.12.

TODO:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• New/modified features documented in docs/tutorial.rst
• Changes documented in docs/release.rst
• GitHub Actions have all passed
• Test coverage is 100% (Codecov passes)

[joshmoore]

Note: green builds will require updating the GitHub settings

[d-v-b]

this is great idea, thank you

[joshmoore]

May have been a bit premature with 3.12...

      error: command '/usr/bin/gcc' failed with exit code 1
      [end of output]
  
  note: This error originates from a subprocess, and is likely not a problem with pip.
  ERROR: Failed building wheel for line_profiler

see: pyutils/line_profiler#247

[joshmoore]

All non-3.8 builds have passed. I think this is in a fine state. @jakirkham, any thoughts, after you recently added 3.12 to numcodecs but didn't drop 3.8?

[jhamman]

+1 on dropping 3.8 then 3.9 early next year. @joshmoore - can we help you get this over the line?

[joshmoore]

I accepted your change, @jhamman, and merged in main. Assuming all is green, I imagine we can get this in immediately (unless we want one last pre-drop release).

[jhamman]

I accepted your change, @jhamman, and merged in main. Assuming all is green, I imagine we can get this in immediately (unless we want one last pre-drop release).

I don't think that is necessary. Let's merge when this goes green!

[jhamman]

@joshmoore - any idea why the last few checks have not reported back?

[joshmoore]

Got a (big) verbal 👍 from @jakirkham. The failing jobs are due to the job configuration re: #1557 (comment)

I'll merge now and bump the 3.8s to 3.9s.

[joshmoore]

For now I've bumped the Windows and just removed the build items since the new versions hadn't been built yet: