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/GuestShaderCacheHeader.cs

@@ -0,0 +1,42 @@
+using System.Runtime.InteropServices;
+
+namespace Ryujinx.Graphics.Gpu.Shader.Cache.Definition
+{
+    /// <summary>
+    /// The header of a shader program in the guest cache.
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential, Pack = 0x1, Size = 0x10)]
+    struct GuestShaderCacheHeader
+    {
+        /// <summary>
+        /// The count of shaders defining this program.
+        /// </summary>
+        public byte Count;
+
+        /// <summary>
+        /// The count of transform feedback data used in this program.
+        /// </summary>
+        public byte TransformFeedbackCount;
+
+        /// <summary>
+        /// Unused/reserved.
+        /// </summary>
+        public ushort Reserved1;
+
+        /// <summary>
+        /// Unused/reserved.
+        /// </summary>
+        public ulong Reserved2;
+
+        /// <summary>
+        /// Create a new guest shader cache header.
+        /// </summary>
+        /// <param name="count">The count of shaders defining this program</param>
+        /// <param name="transformFeedbackCount">The count of transform feedback data used in this program</param>
+        public GuestShaderCacheHeader(byte count, byte transformFeedbackCount) : this()
+        {
+            Count = count;
+            TransformFeedbackCount = transformFeedbackCount;
+        }
+    }
+}