Revert the Metal Experiment (#701)

Metal sounded like a good idea to get in the emulator but frankly I
underestimated just how experimental and not ready it was.
From my write up in the Discord:
```
As is, Metal supports only a few games.
The games it does support freeze on first use of not playing them via Vulkan, because shader translation is broken.
So you need to use a dirty hack to not delete all your shaders.
Not to mention it breaks many games via MoltenVK because of changes to the shared GPU code.

Merging Metal seemed like a great idea, because of the few games it does support.
But I don't think it's worth it. Many of the games it breaks via MoltenVK *don't work via Metal*. 
Which effectively makes current Ryubing worse for Mac users than Ryujinx 1.1.1403.

I think what I'm gonna do is revert Metal, and reopen it as a PR. That way, you can still take advantage of the Metal backend as is, but without making other games worse with no solution.
```

For what it's worth, the shader translation part could at least be
"fixed" by always applying a 30ms delay for shader translation to Metal.
That being said, that solution sucks ass.
The MoltenVK regressions are even worse.



I hope this is not a let down to the Mac users. I hope you realize I'm
reverting this because you're actively getting a worse experience with
it in the emulator.

src/Ryujinx.Graphics.Shader/CodeGen/Msl/Instructions/InstGenCall.cs

@@ -1,60 +0,0 @@
-using Ryujinx.Graphics.Shader.StructuredIr;
-
-using static Ryujinx.Graphics.Shader.CodeGen.Msl.Instructions.InstGenHelper;
-
-namespace Ryujinx.Graphics.Shader.CodeGen.Msl.Instructions
-{
-    static class InstGenCall
-    {
-        public static string Call(CodeGenContext context, AstOperation operation)
-        {
-            AstOperand funcId = (AstOperand)operation.GetSource(0);
-
-            StructuredFunction function = context.GetFunction(funcId.Value);
-
-            int argCount = operation.SourcesCount - 1;
-            int additionalArgCount = CodeGenContext.AdditionalArgCount + (context.Definitions.Stage != ShaderStage.Compute ? 1 : 0);
-            bool needsThreadIndex = false;
-
-            // TODO: Replace this with a proper flag
-            if (function.Name.Contains("Shuffle"))
-            {
-                needsThreadIndex = true;
-                additionalArgCount++;
-            }
-
-            string[] args = new string[argCount + additionalArgCount];
-
-            // Additional arguments
-            if (context.Definitions.Stage != ShaderStage.Compute)
-            {
-                args[0] = "in";
-                args[1] = "constant_buffers";
-                args[2] = "storage_buffers";
-
-                if (needsThreadIndex)
-                {
-                    args[3] = "thread_index_in_simdgroup";
-                }
-            }
-            else
-            {
-                args[0] = "constant_buffers";
-                args[1] = "storage_buffers";
-
-                if (needsThreadIndex)
-                {
-                    args[2] = "thread_index_in_simdgroup";
-                }
-            }
-
-            int argIndex = additionalArgCount;
-            for (int i = 0; i < argCount; i++)
-            {
-                args[argIndex++] = GetSourceExpr(context, operation.GetSource(i + 1), function.GetArgumentType(i));
-            }
-
-            return $"{function.Name}({string.Join(", ", args)})";
-        }
-    }
-}