now that we have per-host custom tests, it does not make sense anymore
to have magic lumpsum tests.
users are encouraged to use the new digga.lib.allProfilesTest standard
test and add it to a host's test like so:
`nixos.<host>.tests = [ digga.lib.allPrefilesTest ];`
In this changeset, the `self` module argument is not actually passed.
Upstream nixpkgs, for unknown reasons does not fail with the usual
error message, presumably becuase this is sumoduleWith type, but instead
bails with an inifinite recursion.
