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-on-droid/cheetah/configuration.nix

@@ -0,0 +1,38 @@
+{ inputs, lib, pkgs, config, ... }:
+
+{
+  environment.packages = with pkgs; [ ];
+
+  # Backup etc files instead of failing to activate generation if a file already exists in /etc
+  environment.etcBackupExtension = ".bak";
+
+  # Remove motd
+  environment.motd = null;
+
+  # # Set $EDITOR
+  # environment.variables.EDITOR = "nvim";
+
+  user.shell = "${pkgs.zsh}/bin/zsh";
+
+  # Read the changelog before changing this value
+  system.stateVersion = "22.11";
+
+  nix.extraOptions = ''
+    experimental-features = nix-command flakes recursive-nix
+    keep-outputs = true
+    keep-derivations = true
+  '';
+
+  nix.package = pkgs.nixVersions.monitored.latest;
+
+  time.timeZone = "Europe/Sofia";
+
+  terminal.font =
+    let
+      firacode = pkgs.nerdfonts.override {
+        fonts = [ "FiraCode" ];
+      };
+      fontPath = "share/fonts/truetype/NerdFonts/FiraCodeNerdFontMono-Regular.ttf";
+    in
+    "${firacode}/${fontPath}";
+}