MAINT: NEP29 for Apr 2024, GitHub Actions updates

[jklenzing]

Description

• Updates NEP29 for April 2024
• Updates GitHub Actions workflows to use latest versions of python, etc

Note that historically, we have not included the operational environment tests here. 🧟

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

via GitHub Actions, including manual jobs here:
with pysat RC
with optional RCs - known bugs for apexpy, OMMBV installs (usage of OMMBV is deprecated)
pip RC install

Test Configuration

• Operating system: Windows, linux, mac
• Version number: Python 3.10, 3.11, 3.12
• numpy 1.23, latest

Checklist:

• Make sure you are merging into the develop (not main) branch
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• Add a note to CHANGELOG.md, summarizing the changes
• Update zenodo.json file for new code contributors

If this is a release PR, replace the first item of the above checklist with the
release checklist on the pysat wiki:
https://github.com/pysat/pysat/wiki/Checklist-for-Release