Refactor render graph: modular compilation & execution

Major overhaul of render graph system for modularity and performance:
- Split compilation and execution logic into dedicated classes (Compiler, Executor, NativePassBuilder, Barriers)
- Overhauled barrier system: now uses CompiledBarrier with target state only, querying before state at execution
- Resource size/alignment now queried from D3D12 device for accurate heap allocation
- ResourceDesc now includes Type field and asserts correct union access
- Centralized D3D12 interop logic in D3D12Utility extensions
- Added RenderGraphHasher for structural graph hashing and cache invalidation
- RenderGraph class simplified to orchestrate specialized components
- ResourceAliasingManager now uses allocator for size queries
- Compilation cache now stores compiled barriers, reducing memory usage
- Improved comments, debug assertions, and removed redundant code

Result: more maintainable, efficient, and robust render graph pipeline.

Ghost.Graphics/RHI/IResourceAllocator.cs

@@ -69,8 +69,23 @@ public struct AllocationDesc
     }
 }
 
+public readonly struct ResourceSizeInfo
+{
+    public ulong Size
+    {
+        get; init;
+    }
+
+    public ulong Alignment
+    {
+        get; init;
+    }
+}
+
 public interface IResourceAllocator : IDisposable
 {
+    ResourceSizeInfo GetSizeInfo(ResourceDesc desc);
+
     /// <summary>
     /// Allocates a block of memory on the GPU
     /// </summary>