Enable Windows CI Running Tests on AppVeyor

[WardF]

When last checked, ctest would hang immediately on AppVeyor. Running by hand is problematic (and has been for a while), so let's get this sorted out.

[dopplershift]

Any particular reason to use AppVeyor and not GitHub Actions?

[WardF]

Appveyor is what we had originally and if it just works, now, that's enough for the moment until we get these other things taken care of. If appveyor still hangs, then I will take the time to move us over to GitHub actions based. It will be (more of a) hassle but it will also speed things up by eliminating the need to double check things by hand.