fix: RHI抽象层单元测试修复

- 实现 D3D12Device::CreateCommandQueue/CreateCommandList/CreateSwapChain
- 修复 Buffer::Map 对 DEFAULT heap 的问题 (Vertex/Index 使用 UPLOAD heap)
- 修复 Fence::IsSignaled() 初始值问题
- 修复 Sampler::GetNativeHandle() 返回值
- 修复 RHICapabilities 和 RHIDeviceInfo 初始化
- 修复 Shader 测试 (空 ShaderCompileDesc 预期)
- 修复 RHITestFixture 创建窗口句柄
- 重命名 opengl_engine_tests -> rhi_opengl_tests
- 添加 tests/RHI/unit/ 到构建系统

测试结果: 22 passed -> 59 passed

engine/include/XCEngine/RHI/D3D12/D3D12Device.h

@@ -103,12 +103,14 @@ private:
     ComPtr<ID3D12Device> m_device;
     ComPtr<IDXGIFactory4> m_factory;
     ComPtr<IDXGIAdapter1> m_adapter;
+    ComPtr<ID3D12CommandQueue> m_commandQueue;
     
     AdapterInfo m_adapterInfo;
     RHICapabilities m_capabilities;
     RHIDeviceInfo m_deviceInfo;
     bool m_isDeviceRemoved;
     bool m_initialized;
+    RHIDeviceDesc m_deviceDesc;
 };
 
 } // namespace RHI

engine/include/XCEngine/RHI/D3D12/D3D12Fence.h

@@ -31,7 +31,7 @@ public:
 private:
     ComPtr<ID3D12Fence> m_fence;
     void* m_eventHandle;
-    uint64_t m_signalValue = 0;
+    uint64_t m_signalValue = UINT64_MAX;
 };
 
 } // namespace RHI

engine/include/XCEngine/RHI/D3D12/D3D12Sampler.h

@@ -21,14 +21,15 @@ public:
 
     D3D12_SAMPLER_DESC GetDesc() const { return m_desc; }
 
-    void* GetNativeHandle() override { return nullptr; }
-    unsigned int GetID() override { return 0; }
+    void* GetNativeHandle() override { return &m_desc; }
+    unsigned int GetID() override { return m_id; }
 
     void Bind(unsigned int unit) override { }
     void Unbind(unsigned int unit) override { }
 
 private:
     D3D12_SAMPLER_DESC m_desc;
+    unsigned int m_id = 0;
 };
 
 } // namespace RHI