Vulkan: Use templates for descriptor updates (#6014)

* WIP: Descriptor template update

* Make configurable

* Wording

* Simplify template creation

* Whitespace

* UTF-8 whatever

* Leave only templated path, better template updater

src/Ryujinx.Graphics.Vulkan/DescriptorSetTemplateUpdater.cs

@@ -0,0 +1,65 @@
+using Ryujinx.Common;
+using Silk.NET.Vulkan;
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace Ryujinx.Graphics.Vulkan
+{
+    ref struct DescriptorSetTemplateWriter
+    {
+        private Span<byte> _data;
+
+        public DescriptorSetTemplateWriter(Span<byte> data)
+        {
+            _data = data;
+        }
+
+        public void Push<T>(ReadOnlySpan<T> values) where T : unmanaged
+        {
+            Span<T> target = MemoryMarshal.Cast<byte, T>(_data);
+
+            values.CopyTo(target);
+
+            _data = _data[(Unsafe.SizeOf<T>() * values.Length)..];
+        }
+    }
+
+    unsafe class DescriptorSetTemplateUpdater : IDisposable
+    {
+        private const int SizeGranularity = 512;
+
+        private DescriptorSetTemplate _activeTemplate;
+        private NativeArray<byte> _data;
+
+        private void EnsureSize(int size)
+        {
+            if (_data == null || _data.Length < size)
+            {
+                _data?.Dispose();
+
+                int dataSize = BitUtils.AlignUp(size, SizeGranularity);
+                _data = new NativeArray<byte>(dataSize);
+            }
+        }
+
+        public DescriptorSetTemplateWriter Begin(DescriptorSetTemplate template)
+        {
+            _activeTemplate = template;
+
+            EnsureSize(template.Size);
+
+            return new DescriptorSetTemplateWriter(new Span<byte>(_data.Pointer, template.Size));
+        }
+
+        public void Commit(VulkanRenderer gd, Device device, DescriptorSet set)
+        {
+            gd.Api.UpdateDescriptorSetWithTemplate(device, set, _activeTemplate.Template, _data.Pointer);
+        }
+
+        public void Dispose()
+        {
+            _data?.Dispose();
+        }
+    }
+}