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.Shader/ShaderStage.cs

@@ -1,12 +1,14 @@
 namespace Ryujinx.Graphics.Shader
 {
-    public enum ShaderStage
+    public enum ShaderStage : byte
     {
         Compute,
         Vertex,
         TessellationControl,
         TessellationEvaluation,
         Geometry,
-        Fragment
+        Fragment,
+
+        Count
     }
 }