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/D3D12/D3D12ResourceDatabase.cs

@@ -294,7 +294,6 @@ internal class D3D12ResourceDatabase : IResourceDatabase
         }
 
         info.Release(_descriptorAllocator);
-        //System.Diagnostics.Debug.Assert(info.Release(_descriptorAllocator) == 0);
 #if DEBUG || GHOST_EDITOR
         _resourceName.Remove(handle, out var name);
 #endif