The options API has been updated, in order for a more flexible setup
with `local.modules.desktop.enable` being replaced with an enum of
desktops at `local.systemVars.desktop`, which allows for switching
desktop environments by changing a single option. This is so that we can
switch to cosmic and only enable the programs we need (i.e. disable
greetd because we use cosmic-greeter and enable terminals since that is
desktop related). This is simpler than having a different module per
desktop.
As my NixOS configuration kept growing, I noticed that I don't need
home-manager as much as I did before. A lot of what I need is just a way
to map nix attrsets to the program's respective configuration format,
which is something that I can now do myself, as my nix knowledge got
more extensive. After all of this, I decided to completely get rid of
home-manager, and switch to a simpler solution called hjem, which just
lets me write files to my home directory that are automatically
symlinked using `systemd-tmpfiles`.
This allows me to simplify my configuration, remove the separation
between NixOS and home-manager modules, and cut my eval times by quite a
lot (which allows for faster `nixos-rebuild switch`!).
