Remove use of macOS-12; add explicit use of system python

[freakboy3742]

A collection of CI updates reflecting platform changes:

1. macOS-12 runners will be turned off in just over a month, so we should stop using them. macOS-13 is the last x86-64 runner that is available; macOS-latest will be ARM64 from now on.
2. Enable allow-prereleases on all Python installs. .github#172 adds the ability to explicitly reference a "system" python, rather than pinning the Ubuntu release and ensuring the python-version matches the Ubuntu release.

PR Checklist:

• All new features have been tested
• All new features have been documented
• I have read the CONTRIBUTING.md file
• I will abide by the code of conduct

[rmartin16]

2 comments

[rmartin16]

👍🏼

Looks good. On a sidenote, I realized we're not actually using the logic in app-create-verify to skip actions/setup-python anywhere since we never pass system for python-version to it. I don't think that's a problem, though.