Run more Playground CLI tests on Windows and macOS

[brandonpayton]

Motivation for the change, related issues

Our full Playground CLI test suite does not run on Windows and macOS. Let's fix this so we have more complete test coverage across supported platforms.

Implementation details

TBD

Testing Instructions (or ideally a Blueprint)

• CI

[brandonpayton]

NOTE: The macOS runner is sometimes failing in prepare-playground with:

Error: The template is not valid. /Users/runner/work/wordpress-playground/wordpress-playground/./.github/actions/prepare-playground/action.yml (Line: 27, Col: 20): hashFiles('package-lock.json') failed. Fail to hash files under directory '/Users/runner/work/wordpress-playground/wordpress-playground'

Apparently, this is an intermittent issue with the macOS runner on GitHub right now:
actions/runner-images#13341

[brandonpayton]

The good news is that when prepare-playground doesn't fail, the Playground CLI test suite appears to be succeeding in macOS now. It wasn't earlier this year. We were running into something like open file descriptor limits.

[brandonpayton]

Apparently, this is an intermittent issue with the macOS runner on GitHub right now:
actions/runner-images#13341

According to this comment, they've applied a workaround and are working on a long term fix, so there shouldn't be an issue here.