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/Managers/SceneManager.h

@@ -14,13 +14,14 @@
 #include <XCEngine/Scene/Scene.h>
 
 #include "Core/ISelectionManager.h"
+#include "Core/ISceneManager.h"
 
 namespace XCEngine {
 namespace Editor {
 
 class ISelectionManager;
 
-class SceneManager {
+class SceneManager : public ISceneManager {
 public:
     SceneManager();