The new test runner will evaluate all test profiles from the README.md
in parallel in separate nix-build processes.
Since we do not load all processes into one process,
this also helps saving memory.
nix-env picked up `default.nix`, which contained our hardware profiles.
This is not only cpu-intensive to evaluate but also fails because
it does some import-from-derivation.
By moving default.nix to release.nix it should be no longer loaded