feat(configurations)!: flatten down, introduce meta.nix

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`

hosts/nix-darwin/apavel-a01/configuration.nix

@@ -0,0 +1,32 @@
+{ inputs, lib, pkgs, config, ... }:
+
+{
+  environment.systemPackages = with pkgs; [ ];
+
+  # environment.darwinConfig = builtins.toString ./configuration.nix;
+
+  # Auto upgrade nix package and the daemon service.
+  services.nix-daemon.enable = true;
+
+  nix.package = pkgs.nix;
+
+  # Create /etc/zshrc that loads the nix-darwin environment.
+  programs.zsh.enable = true; # default shell on catalina
+
+  # Fonts
+  fonts.fontDir.enable = true;
+  fonts.fonts = with pkgs; [
+    (nerdfonts.override { fonts = [ "FiraCode" ]; })
+  ];
+
+  # Keyboard
+  system.keyboard.enableKeyMapping = true;
+  system.keyboard.remapCapsLockToEscape = true;
+
+  # Add ability to used TouchID for sudo authentication
+  security.pam.enableSudoTouchIdAuth = true;
+
+  # Used for backwards compatibility, please read the changelog before changing.
+  # > darwin-rebuild changelog
+  system.stateVersion = 4;
+}