feat: Implement D3D12 resource factory and improve swap chain management

- Added D3D12ResourceFactory for creating render targets, textures, and buffers.
- Enhanced D3D12SwapChain to manage back buffer render targets and provide access to them.
- Updated D3D12Texture to utilize resource handles for better resource management.
- Removed legacy ResourceAllocator and integrated improvements for resource handling.
- Introduced new interfaces for resource factory and swap chain to streamline resource creation.
- Added support for mip levels and texture dimensions in render target and texture descriptions.
- Created new markdown files to document allocator and swap chain improvements.

Ghost.Graphics/Data/ResourceHandle.cs

@@ -81,6 +81,8 @@ public readonly struct TextureHandle : IEquatable<TextureHandle>, IDisposable
 
     internal ResourceHandle ResourceHandle => _resourceHandle;
 
+    public static TextureHandle Invalid => new(ResourceHandle.Invalid);
+
     internal TextureHandle(ResourceHandle resourceHandle)
     {
         _resourceHandle = resourceHandle;
@@ -125,6 +127,8 @@ public readonly struct BufferHandle : IEquatable<BufferHandle>, IDisposable
 
     internal ResourceHandle ResourceHandle => _resourceHandle;
 
+    public static BufferHandle Invalid => new(ResourceHandle.Invalid);
+
     internal BufferHandle(ResourceHandle resourceHandle)
     {
         _resourceHandle = resourceHandle;