get rid of test.cmd

[nohwnd]

test.cmd makes some things easier in arcade, but the api is clunky and non-standard, we probably want to use the standard tools (like dotnet test directly), and avoid custom scripts that shield us from how general repos do it, and from the user experience users have.

If more development will happen in this repo, consider moving the top level testing back to vstest, to use the experience user will see and drive change.