Create ISceneManager interface and fix GetSceneManager return type

- Created ISceneManager interface with Editor需要的 SceneManager 方法
- SceneManager now implements ISceneManager
- IEditorContext::GetSceneManager() now returns ISceneManager& instead of void*
- Removed SceneManager::GetSceneManagerConcrete() method
- Updated HierarchyPanel and InspectorPanel to use ISceneManager interface

editor/src/Core/IEditorContext.h

@@ -9,6 +9,7 @@ namespace Editor {
 class EventBus;
 class ISelectionManager;
 class IProjectManager;
+class ISceneManager;
 
 class IEditorContext {
 public:
@@ -16,7 +17,7 @@ public:
     
     virtual EventBus& GetEventBus() = 0;
     virtual ISelectionManager& GetSelectionManager() = 0;
-    virtual void* GetSceneManager() = 0;
+    virtual ISceneManager& GetSceneManager() = 0;
     virtual IProjectManager& GetProjectManager() = 0;
     
     virtual void SetProjectPath(const std::string& path) = 0;