turn on coffea tests when CoffeaTeam/coffea#882 is merged

[lgray]

Right now coffea tests take a rather long amount of time, but the mentioned PR, scikit-hep/coffea#882, vastly reduces testing so that we can always run all tests.

[jpivarski]

For some reason, I couldn't use micromamba to install ROOT, so I used the standard miniconda action, and there's no caching for compiling awkward-cpp. I took that out to get it working and not get confused by hold-overs from previous runs.

If you want to do some big 20 or 30 minute test of a distributed job in Coffea, then this is appropriate. It can run once a day (using up 6 test runners), and that would be fine. When integration fails, we shouldn't try to debug it in the GitHub Action, but in a local checkout. (I'm expecting this to catch incompatibilities introduced in the latest version of one of these four packages, which shouldn't appear in Windows-only, which is the only one I don't know how to debug outside of GitHub Actions.)