feat: implement descriptor heap with thread-safe allocation

D3D12 Resources:
- Add descriptor_handle struct with CPU/GPU handles
- Add descriptor_heap class for descriptor management
- Implement allocate() and free() methods
- Add mutex for thread-safe access
- Support all D3D12 descriptor heap types

D3D12 Core:
- Add device() function to expose main device
- Add release() template function for COM objects

Documentation:
- Add changelog for descriptor heap implementation
- Update D3D12 Wiki with descriptor heap section
- Mark descriptor heap task as completed

Engine/Graphics/Direct3D12/D3D12Resources.h

@@ -0,0 +1,67 @@
+#pragma once
+#include "D3D12CommonHeaders.h"
+
+namespace XEngine::graphics::d3d12{
+class descriptor_heap;
+struct descriptor_handle
+{
+    D3D12_CPU_DESCRIPTOR_HANDLE cpu{};
+    D3D12_GPU_DESCRIPTOR_HANDLE gpu{};
+
+    constexpr bool is_valid() const { return cpu.ptr != 0; }
+    constexpr bool is_shader_visible() const { return gpu.ptr != 0; }
+#ifdef _DEBUG
+private:
+    friend class descriptor_heap;
+    descriptor_heap*    container{ nullptr };
+    u32                 index{ u32_invalid_id };       
+#endif
+}; // descriptor_handle
+class descriptor_heap
+{
+public:
+    explicit descriptor_heap(const D3D12_DESCRIPTOR_HEAP_TYPE type): _type(type){}
+    DISABLE_COPY_AND_MOVE(descriptor_heap);
+    ~descriptor_heap(){assert(!_heap);}
+
+    bool initialize(u32 capacity, bool is_shader_visible);
+    void release();
+
+    [[nodiscard]] descriptor_handle allocate();
+    void free(descriptor_handle handle);
+
+    constexpr D3D12_DESCRIPTOR_HEAP_TYPE type() const { return _type; }
+    constexpr D3D12_CPU_DESCRIPTOR_HANDLE cpu_start() const { return _cpu_start; }
+    constexpr D3D12_GPU_DESCRIPTOR_HANDLE gpu_start() const { return _gpu_start; }
+    constexpr ID3D12DescriptorHeap *const heap() const { return _heap; }
+    constexpr u32 capacity() const { return _capacity; }
+    constexpr u32 size() const { return _size; }
+    constexpr u32 descriptor_size() const { return _descriptor_size; }
+    constexpr bool is_shader_visible() const { return _gpu_start.ptr != 0; }
+private:
+    // 一个描述符堆是一个内存块,基于他是否着色器可见,分配在系统内存还是显存
+    ID3D12DescriptorHeap*                   _heap;
+
+    // CPU起始句柄（用于CPU端描述符操作）
+    D3D12_CPU_DESCRIPTOR_HANDLE             _cpu_start{};
+    // GPU起始句柄（仅当堆为着色器可见时有效）
+    D3D12_GPU_DESCRIPTOR_HANDLE             _gpu_start{};
+
+    // 空闲的描述符句柄
+    std::unique_ptr<u32[]>                  _free_handles{};
+
+    // 用于保护资源初始化的互斥锁
+    std::mutex                              _mutex; 
+
+    // 描述符堆的容量
+    u32                                     _capacity{0};
+    // 已经分配的描述符数量
+    u32                                     _size{0};
+    // 不同的描述符堆类型在不同的硬件上有不同的大小,所以需要记录下描述符的大小
+    u32                                     _descriptor_size{0};
+    const D3D12_DESCRIPTOR_HEAP_TYPE        _type;
+};
+}
+
+
+