Refactor user option types across modules for consistency

Updated multiple configuration files to replace the user option type with a unified `usersOptionType`, enhancing consistency in user management across applications and services. This change simplifies the user configuration process and improves maintainability.

modules/dev/emacs.nix

@@ -9,9 +9,8 @@
   options.my.emacs = {
     enable = lib.mkEnableOption "Doom Emacs configuration";
     users = lib.mkOption {
-      type = lib.types.either lib.types.str (lib.types.listOf lib.types.str);
+      type = inputs.self.lib.usersOptionType lib;
       default = config.my.toggleUsers.dev;
-      merge = inputs.self.lib.mergeUsersOption lib;
       description = "Users to install Emacs packages for";
     };
   };