refactor: rename _AppConfigFetchRequested event

- Renamed to AppConfigFetchRequested
- Made event public

Author: fulleni

lib/app/bloc/app_event.dart

@@ -92,12 +92,12 @@ class AppTextScaleFactorChanged extends AppEvent {
   List<Object?> get props => [appTextScaleFactor];
 }
 
-/// {@template _app_config_fetch_requested}
-/// Internal event to trigger fetching of the global AppConfig.
+/// {@template app_config_fetch_requested}
+/// Event to trigger fetching of the global AppConfig.
 /// {@endtemplate}
-class _AppConfigFetchRequested extends AppEvent {
-  /// {@macro _app_config_fetch_requested}
-  const _AppConfigFetchRequested();
+class AppConfigFetchRequested extends AppEvent {
+  /// {@macro app_config_fetch_requested}
+  const AppConfigFetchRequested();
 }
 
 /// {@template app_user_account_action_shown}