Let's consolidate all modules under one path, so that NixOS,
home-manager, and nix-darwin (if I ever end up using it down the line)
would go under the same folder.
Steam wants to pollute HOME with `.steam*` files and folders, which are
useless and annoying.
We want to make sure the wrappers are preferred when installing, so use
`lib.hiPrio` to ensure they get chosen.