Reallocate Windows test runners to test on WSL2

[rfay]

Now that Windows 10 2020 Spring is here, all Windows users can use Docker Desktop. That means we will cease support for Docker Toolbox, see #2284

But we can use our windows machines more effectively:

• All should be the same class of machine (a generic pool of Windows 10)
• All should be able to run tests in WSL2 or Windows-side

Don't forget that Quicksprint depends (currently) on docker toolbox, drud/quicksprint#174 will remove it.
I think the build-tools tests also test toolbox.

[rfay]

The two docker toolbox Windows test machines have been converted to generic WIndows, no more toolbox.

[rfay]

This will end up being a task for the move to github actions; we'll end up doing Windows on github actions.