This core will be used as the new base for the reuse branch, which is
essentiall the same as the existing template branch, except that it is
rebased from this core, simplifying future rebasing.
* Import attrs of profiles automatically with `defaultImport`.
* Refactor profiles to ensure all are functions returning a module.
* Add a suites.nix with collections of profiles.
* Add suites as `specialArgs` to modules.
* Add suite import to NixOS host.
