Add CI for macOS

[bennibbelink]

Cyclus supports macOS, we should add CI workflows in this repo as well.

[bennibbelink]

Doubling back to this (and cyclus/cycamore#631) there are a few ways to go about it:

1. Add a macos_build_test.yml to cyclus/cycamore and cyclus/cymetric that use the cyclus_dev (and cycamore_dev in the case of cymetric) conda packages and build/test off of those so the workflow doesn't completely rebuild cyclus. This requires that we resolve Add CI to trigger feedstock rebuild on push to main cyclus#1834 to ensure the feedstock is always up to date with our main branch. This is the most complete/thorough of the 3 options, but adds some complexity to the CI.
2. Only build/test cyclus/cyclus in the cyclus/cyclus CI, similar to our support for Rocky linux. This would require no further changes, but we could run into issues downstream.
3. Build/test all three repositories in cyclus/cyclus, similar to our CI for Ubuntu. I'm not sure how much value this adds, since that strategy is intended to expose changes that break downstream projects, and is less focused on architecture support.

Wanted to open this up for discussion before implementing any unwanted/unnecessary infrastructure, @gonuke what are your thoughts?