Rework SVC handling (#883)

* Rework SVC handling

Prepare for 32 bits support.

* QueryMemory64 x1 is an output

* Pregenerate all SVC handler

Also clean up + 32 bits code path

* Address gdk's comments

* Simplify local setter loop

* Address jd's comments

Ryujinx.HLE/HOS/Kernel/SupervisorCall/RAttribute.cs

@@ -0,0 +1,15 @@
+using System;
+
+namespace Ryujinx.HLE.HOS.Kernel.SupervisorCall
+{
+    [AttributeUsage(AttributeTargets.Parameter, AllowMultiple = false)]
+    public class RAttribute : Attribute
+    {
+        public readonly int Index;
+
+        public RAttribute(int index)
+        {
+            Index = index;
+        }
+    }
+}