Implement CAL and RET shader instructions (#1618)

* Add support for CAL and RET shader instructions

* Remove unused stuff

* Fix a bug that could cause the wrong values to be passed to a function

* Avoid repopulating function id dictionary every time

* PR feedback

* Fix vertex shader A/B merge

Ryujinx.Graphics.Shader/IntermediateRepresentation/OperandHelper.cs

@@ -5,6 +5,11 @@ namespace Ryujinx.Graphics.Shader.IntermediateRepresentation
 {
     static class OperandHelper
     {
+        public static Operand Argument(int value)
+        {
+            return new Operand(OperandType.Argument, value);
+        }
+
         public static Operand Attribute(int value)
         {
             return new Operand(OperandType.Attribute, value);