Speed up GitHub workflows

[bkeryan]

• This contribution adheres to CONTRIBUTING.md.

What does this Pull Request accomplish?

• Caching improvements
  • Cache in-project virtualenvs. All of our caching code was still using ~/.cache/pypoetry/virtualenvs.
  • I originally tried using actions/setup-python's built-in caching, but I ran into two problems:
    • It requires installing Poetry before Python (e.g. with pipx), and when I did this, tests used the wrong Python version. (pipx is slightly faster than Gr1N/setup-poetry, though.)
    • Its cache key setup is limited to simple use cases and can't handle optional extras or Poetry dependency groups.
  • Use restore/save for workflows that run poetry install multiple times with different extras and/or dependency groups.
  • Cache example poetry.lock files. These lock files are not checked into Git, but generating them takes over 5 minutes, so they are worth caching.
  • For system tests, cache the .tox directory as well. Caching on the self-hosted runner has significant overhead, but it seems to be an overall win compared to installing from PyPI for each Python version.
  • Remove caching from Publish_NIMS.yml. We don't run this workflow very often and it's better to avoid a possible source of failure.
• Disable unit tests on macOS
  • Running tests on macOS often takes longer than on Linux and Windows
  • Caching virtualenvs on macOS was returning errors about invalid/corrupted virtualenvs. Maybe this was because I was skipping poetry install on cache hits at the time, but I don't want to spend any more time on it.

Why should this Pull Request be merged?

Speed up builds (when there is a cache hit):

• Check NIMG: 1 min -> 30 sec
• Check NIMS: 2 min 30 sec -> 1 min 15 sec
• Check examples: 12-15 min -> 2 min 30 sec
• Run unit tests (Linux): 3 min -> 2 min
• Run unit tests (Windows): 4-6 min -> 3-4 min
• Run system tests: 21-23 min -> 15-16 min (not counting time to scale up new runner instance)
• Total run time: 2 hr -> 1 hr
• Total duration: 40 min -> 22 min

What testing has been done?

Ran PR workflow.

[github-actions]

Test Results

       30 files   -      10         30 suites   - 10   38m 14s ⏱️ - 9m 33s
     479 tests ±       0       479 ✔️ ±       0         0 💤 ±    0  0 ❌ ±0 
12 290 runs   - 3 820  11 230 ✔️  - 3 280  1 060 💤  - 540  0 ❌ ±0 

Results for commit af161a1. ± Comparison against base commit e7b2b6d.

♻️ This comment has been updated with latest results.