Fix macOS CI

[BenWibking]

PR Summary

This fixes the GitHub macOS CI and adds a root-level requirements.txt file for Python package dependencies.

PR Checklist

• [ ] Code passes cpplint
• [ ] New features are documented.
• [ ] Adds a test for any bugs fixed. Adds tests for new features.
• [ ] Code is formatted
• [ ] Changes are summarized in CHANGELOG.md
• [ ] Change is breaking (API, behavior, ...)
  • [ ] Change is additionally added to CHANGELOG.md in the breaking section
  • [ ] PR is marked as breaking
  • [ ] Short summary API changes at the top of the PR (plus optionally with an automated update/fix script)
• [ ] CI has been triggered on Darwin for performance regression tests.
• [ ] Docs build
• [ ] (@lanl.gov employees) Update copyright on changed files

[BenWibking]

@Yurlungur Any ideas on why the macOS CI isn't triggered? 😕

Edit: nevermind, figured it out: https://github.com/parthenon-hpc-lab/parthenon/actions/workflows/ci-macos.yml

[BenWibking]

hmm, we might need to add a requirements.txt file for the python modules:

Error: No file in /Users/runner/work/parthenon/parthenon matched to [**/requirements.txt or **/pyproject.toml], make sure you have checked out the target repository

[Yurlungur]

hmm, we might need to add a requirements.txt file for the python modules:

Error: No file in /Users/runner/work/parthenon/parthenon matched to [**/requirements.txt or **/pyproject.toml], make sure you have checked out the target repository

that's probably worth doing anyway. ;)

[BenWibking]

If the full test suite takes too long on macOS, I will switch to running ctest -LE mpi instead.