feat: 实现 D3D12Sampler 采样器类

- 添加 D3D12Sampler.h/cpp
- 支持采样器描述符
- 测试通过

engine/src/RHI/D3D12Sampler.cpp

@@ -0,0 +1,24 @@
+#include "XCEngine/RHI/D3D12/D3D12Sampler.h"
+
+namespace XCEngine {
+namespace RHI {
+
+D3D12Sampler::D3D12Sampler() {
+    memset(&m_desc, 0, sizeof(D3D12_SAMPLER_DESC));
+}
+
+D3D12Sampler::~D3D12Sampler() {
+    Shutdown();
+}
+
+bool D3D12Sampler::Initialize(ID3D12Device* device, const D3D12_SAMPLER_DESC& desc) {
+    m_desc = desc;
+    return true;
+}
+
+void D3D12Sampler::Shutdown() {
+    memset(&m_desc, 0, sizeof(D3D12_SAMPLER_DESC));
+}
+
+} // namespace RHI
+} // namespace XCEngine