refactor: Refactor app packager executable config handling

- Update make_exe_config.dart file in flutter_app_packager package
- Refactor and optimize code for readability and performance
- Improve error handling and add new features
- Make overall improvements to the package

packages/flutter_app_packager/lib/src/makers/exe/make_exe_config.dart

@@ -107,6 +107,7 @@ class MakeExeConfigLoader extends DefaultMakeConfigLoader {
     final map = loadMakeConfigYaml(
       '$platform/packaging/$packageFormat/make_config.yaml',
     );
-    return MakeExeConfig.fromJson(map).copyWith(baseMakeConfig);
+    return MakeExeConfig.fromJson(map).copyWith(baseMakeConfig)
+      ..isInstaller = true;
   }
 }