feat: 实现 D3D12PipelineState 并替换到 tests/D3D12

- 添加 D3D12PipelineState.h/cpp
- 全局变量 gPipelineState
- 使用 D3D12PipelineState::Initialize 替代原生 CreateGraphicsPipelineState
- 测试通过

engine/include/XCEngine/RHI/D3D12/D3D12PipelineState.h

@@ -0,0 +1,28 @@
+#pragma once
+
+#include <d3d12.h>
+#include <wrl/client.h>
+
+#include "D3D12Enum.h"
+
+using Microsoft::WRL::ComPtr;
+
+namespace XCEngine {
+namespace RHI {
+
+class D3D12PipelineState {
+public:
+    D3D12PipelineState();
+    ~D3D12PipelineState();
+
+    bool Initialize(ID3D12Device* device, const D3D12_GRAPHICS_PIPELINE_STATE_DESC& desc);
+    void Shutdown();
+
+    ID3D12PipelineState* GetPipelineState() const { return m_pipelineState.Get(); }
+
+private:
+    ComPtr<ID3D12PipelineState> m_pipelineState;
+};
+
+} // namespace RHI
+} // namespace XCEngine