major: refactor existing configurations to be more ergonomic

[3ulalia]

As mentioned in 9562884, refactor the configurations of various system components to be more ergonomically included in user configurations.

Currently, modules are strewn across modules/home-manager and modules/nixos, and user configurations of those modules are all over users/[username]. This should be standardized and improved upon. Affected modules include:

niri itself
waybar
swww
gammastep
mako
swaylock
...among others.