feat(generator): support output_dir and build_extensions config for generated files

Now the code generator supports specifying a custom output directory and extension/name template for generated DI files via build.yaml ( and ). This allows placing all generated code in custom folders and using flexible naming schemes.

docs: update all user docs and tutorials to explain new output_dir/build_extensions config

- Added detailed usage and YAML examples to cherrypick_generator/README.md
- Synced full_tutorial_en.md and full_tutorial_ru.md (advanced codegen section) with explanation of new configuration and impact on imports
- Updated quick_start_en.md and quick_start_ru.md to mention advanced customization and point to tutorials
- Added troubleshooting and tips for custom output/imports in docs

examples/postly/lib/app.dart

@@ -7,7 +7,7 @@ import 'domain/repository/post_repository.dart';
 import 'presentation/bloc/post_bloc.dart';
 import 'router/app_router.dart';
 
-part 'app.inject.cherrypick.g.dart';
+part 'generated/app.inject.cherrypick.g.dart';
 
 @injectable()
 class MyApp extends StatelessWidget with _$MyApp {

examples/postly/lib/di/app_module.dart

@@ -5,7 +5,7 @@ import '../data/network/json_placeholder_api.dart';
 import '../data/post_repository_impl.dart';
 import '../domain/repository/post_repository.dart';
 
-part 'app_module.module.cherrypick.g.dart';
+part '../generated/di/app_module.module.cherrypick.g.dart';
 
 @module()
 abstract class AppModule extends Module {