feat(RHI): 在 RHIBuffer 基类中添加资源状态接口

- 添加 GetState() 和 SetState() 纯虚函数到 RHIBuffer 抽象基类
- D3D12Buffer 已有实现，现在通过基类接口可用
- OpenGLBuffer 添加空实现（OpenGL 无资源状态概念）

engine/include/XCEngine/RHI/OpenGL/OpenGLBuffer.h

@@ -51,6 +51,9 @@ public:
 
     void* GetNativeHandle() override { return reinterpret_cast<void*>(static_cast<uintptr_t>(m_buffer)); }
 
+    ResourceStates GetState() const override { return ResourceStates::Common; }
+    void SetState(ResourceStates state) override { }
+
     const std::string& GetName() const override { return m_name; }
     void SetName(const std::string& name) override { m_name = name; }
 

engine/include/XCEngine/RHI/RHIBuffer.h

@@ -23,6 +23,9 @@ public:
 
     virtual void* GetNativeHandle() = 0;
 
+    virtual ResourceStates GetState() const = 0;
+    virtual void SetState(ResourceStates state) = 0;
+
     virtual const std::string& GetName() const = 0;
     virtual void SetName(const std::string& name) = 0;