Salieri: shader cache (#1701)

Here come Salieri, my implementation of a disk shader cache!

"I'm sure you know why I named it that."
"It doesn't really mean anything."

This implementation collects shaders at runtime and cache them to be later compiled when starting a game.

Ryujinx.Graphics.Gpu/Shader/Cache/Definition/GuestShaderCacheEntryHeader.cs

@@ -0,0 +1,67 @@
+using Ryujinx.Graphics.Shader;
+using System.Runtime.InteropServices;
+
+namespace Ryujinx.Graphics.Gpu.Shader.Cache.Definition
+{
+    /// <summary>
+    /// The header of a guest shader entry in a guest shader program.
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential, Pack = 0x1, Size = 0x30)]
+    struct GuestShaderCacheEntryHeader
+    {
+        /// <summary>
+        /// The stage of this shader.
+        /// </summary>
+        public ShaderStage Stage;
+
+        /// <summary>
+        /// Unused/reserved.
+        /// </summary>
+        public byte Reserved1;
+
+        /// <summary>
+        /// Unused/reserved.
+        /// </summary>
+        public byte Reserved2;
+
+        /// <summary>
+        /// Unused/reserved.
+        /// </summary>
+        public byte Reserved3;
+
+        /// <summary>
+        /// The size of the code section.
+        /// </summary>
+        public int Size;
+
+        /// <summary>
+        /// The size of the code2 section if present. (Vertex A)
+        /// </summary>
+        public int SizeA;
+
+        /// <summary>
+        /// Unused/reserved.
+        /// </summary>
+        public int Reserved4;
+
+        /// <summary>
+        /// The header of the cached gpu accessor.
+        /// </summary>
+        public GuestGpuAccessorHeader GpuAccessorHeader;
+
+        /// <summary>
+        /// Create a new guest shader entry header.
+        /// </summary>
+        /// <param name="stage">The stage of this shader</param>
+        /// <param name="size">The size of the code section</param>
+        /// <param name="sizeA">The size of the code2 section if present (Vertex A)</param>
+        /// <param name="gpuAccessorHeader">The header of the cached gpu accessor</param>
+        public GuestShaderCacheEntryHeader(ShaderStage stage, int size, int sizeA, GuestGpuAccessorHeader gpuAccessorHeader) : this()
+        {
+            Stage = stage;
+            Size  = size;
+            SizeA = sizeA;
+            GpuAccessorHeader = gpuAccessorHeader;
+        }
+    }
+}