Run tests on MacOS ARM in CI

[benjyw]

We currently run tests in CI on Linux ARM 64, Linux X86_64, and MacOS X86_64 (we build wheels for all 4 platforms, of course).

However M1 adoption is now very far along, and Darwin X86_64 is, if anything, being phased out. So we should probably test on that platform.

Related: we only run the full test suite on Linux X86_64, and run the "platform specific" test subset on the other two platforms, to save resources. We should probably run the full test suite for all platforms at least on main, if not for every PR.

[sureshjoshi]

TIL we didn't run tests on ARM in CI.

My brain just sees aarch64 and assumes Mac apparently... Damn you Apple! 😆

Some small part of me wants to run limited testing on WSL as well, since any Pants windows users are reliant on that - and I've been finding some weirdness while trying to run the test suites (like, tons of errors, Rule graph problems, etc - unless my logs are somehow causing that 🤷🏽 ).

[huonw]

Prior related investigation/proposal: #20193

[huonw]

Experiment in #20997, potentially blocked by #20998.