Sorry for the kinda big commit that does everything at once
This change does the following:
- yeets skrott and skrot-specific settings from the NixOS module,
- adds a bunch more settings and generalizations to the NixOS module,
- adds two VM NixOS configurations for interactive testing
- wraps the nix package so that `less` is always present in `$PATH`
- yeah, that's about it
kthxbye
