Remove duplication with a reusable workflow

[hugovk]

We can refactor build and build-latest into a single resuable workflow and pass inputs for their differences.

Docs:

• https://github.blog/2021-11-29-github-actions-reusable-workflows-is-generally-available/
• https://docs.github.com/en/actions/using-workflows/reusing-workflows

Not terribly happy with the wheels.yml + wheels-reusable.yml names, suggestions welcome!

---

Also put slower macOS first in the matrix, might speed things up a bit:

-        os: [ "ubuntu-20.04", "macos-latest" ]
+        os: [ "macos-latest", "ubuntu-20.04" ]

And while GHA gives 20 concurrent jobs, I just spotted the limit for macOS is 5:

https://docs.github.com/en/actions/learn-github-actions/usage-limits-billing-and-administration#usage-limits

So another reason to get those queued up sooner.

[radarhere]

My only idea is to refer to what is different between the two calls, the commit, but I'm not sure that wheels-commit.yml sounds any better. commit-workflow.yml maybe?

[hugovk]

Decided on wheels-build.yml for the reusable one, as that does the actual wheel building.

And kept wheels.yml for the main one which is managing the whole wheel stuff.