Flatten down directory structure:
- From: `./hosts/${configuration-type}/${system}/{configuration,deploy}.nix`
- To: `./hosts/${configuration-type}/{meta,configuration}.nix`
Keep `system` and `deploy-rs` config in `meta.nix`
Update `flake.lock`
Also stop passing `outputs` around, prefer `inputs.self`
Also put all `auto_` in `readOnly` `internal` options
- `autoModules`, `autoConfigurations` and `autoPackages`
Do not export packages as overlay (causes an infinite recursion)
- this is documented on the two places it has effect on
-- in `./overlays/default.nix` and `./modules/flake/configurations.nix`
-- in `autoConfigurations` we manually extend `pkgs` with the flake packages
Allow packages to say what `systems` they are compatible with
- See `./pkgs/swww/systems.nix` - disabled for all systems
- See `./pkgs/pngpaste/systems.nix` - enabled only for `darwin` targets
