Make InternalFinalCallback as public so that we can use mockito to mock controll…

…er that extends GetxController

@@ -4,10 +4,10 @@ import '../../get_core/get_core.dart';
 /// overrides if you extend the class that uses it, as Dart has no final
 /// methods.
 /// Used in [DisposableInterface] to avoid the danger of overriding onStart.
-class _InternalFinalCallback<T> {
+class InternalFinalCallback<T> {
   ValueUpdater<T>? _callback;
 
-  _InternalFinalCallback({ValueUpdater<T>? callback}) : _callback = callback;
+  InternalFinalCallback({ValueUpdater<T>? callback}) : _callback = callback;
 
   T call() => _callback!.call();
 }
@@ -26,7 +26,7 @@ mixin GetLifeCycleBase {
   /// It uses an internal "callable" type, to avoid any @overrides in subclases.
   /// This method should be internal and is required to define the
   /// lifetime cycle of the subclass.
-  final onStart = _InternalFinalCallback<void>();
+  final onStart = InternalFinalCallback<void>();
 
   // /// The `configureLifeCycle` works as a constructor for the [GetLifeCycle]
   // ///
@@ -36,7 +36,7 @@ mixin GetLifeCycleBase {
   // }
 
   /// Internal callback that starts the cycle of this controller.
-  final onDelete = _InternalFinalCallback<void>();
+  final onDelete = InternalFinalCallback<void>();
 
   /// Called immediately after the widget is allocated in memory.
   /// You might use this to initialize something for the controller.