Refactor CI workflow

[Lamparter]

This PR splits each CI run into matrixes to make it easier to debug Ironpython builds and make out what's failing.

[Lamparter]

@slozier what do you think?

[slozier]

I don't have an objection to the concept, but unfortunately I don't think it's working as intended. Build is just producing 3x the same package and no tests are running.

I don't think framework arguments have an impact on build or package. And in any case, we want the packages to include binaries for all frameworks so it should not be restricted. I would replace the build step with package and just do a matrix on os.

For the test issues you're going to have to do add back the build step before running the tests.

I guess we end up repeating the build multiple times, but probably going to be faster overall with everything running in parallel?

[Lamparter]

Yes

[slozier]

Looks good to me!

[BCSharp]

This should get rid of all those false positives due to tests not being parallel-safe, it think. 👍