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.Metal/IndexBufferState.cs

@@ -1,103 +0,0 @@
-using Ryujinx.Graphics.GAL;
-using SharpMetal.Metal;
-using System;
-using System.Runtime.Versioning;
-
-namespace Ryujinx.Graphics.Metal
-{
-    [SupportedOSPlatform("macos")]
-    readonly internal struct IndexBufferState
-    {
-        public static IndexBufferState Null => new(BufferHandle.Null, 0, 0);
-
-        private readonly int _offset;
-        private readonly int _size;
-        private readonly IndexType _type;
-
-        private readonly BufferHandle _handle;
-
-        public IndexBufferState(BufferHandle handle, int offset, int size, IndexType type = IndexType.UInt)
-        {
-            _handle = handle;
-            _offset = offset;
-            _size = size;
-            _type = type;
-        }
-
-        public (MTLBuffer, int, MTLIndexType) GetIndexBuffer(MetalRenderer renderer, CommandBufferScoped cbs)
-        {
-            Auto<DisposableBuffer> autoBuffer;
-            int offset, size;
-            MTLIndexType type;
-
-            if (_type == IndexType.UByte)
-            {
-                // Index type is not supported. Convert to I16.
-                autoBuffer = renderer.BufferManager.GetBufferI8ToI16(cbs, _handle, _offset, _size);
-
-                type = MTLIndexType.UInt16;
-                offset = 0;
-                size = _size * 2;
-            }
-            else
-            {
-                autoBuffer = renderer.BufferManager.GetBuffer(_handle, false, out int bufferSize);
-
-                if (_offset >= bufferSize)
-                {
-                    autoBuffer = null;
-                }
-
-                type = _type.Convert();
-                offset = _offset;
-                size = _size;
-            }
-
-            if (autoBuffer != null)
-            {
-                DisposableBuffer buffer = autoBuffer.Get(cbs, offset, size);
-
-                return (buffer.Value, offset, type);
-            }
-
-            return (new MTLBuffer(IntPtr.Zero), 0, MTLIndexType.UInt16);
-        }
-
-        public (MTLBuffer, int, MTLIndexType) GetConvertedIndexBuffer(
-            MetalRenderer renderer,
-            CommandBufferScoped cbs,
-            int firstIndex,
-            int indexCount,
-            int convertedCount,
-            IndexBufferPattern pattern)
-        {
-            // Convert the index buffer using the given pattern.
-            int indexSize = GetIndexSize();
-
-            int firstIndexOffset = firstIndex * indexSize;
-
-            Auto<DisposableBuffer> autoBuffer = renderer.BufferManager.GetBufferTopologyConversion(cbs, _handle, _offset + firstIndexOffset, indexCount * indexSize, pattern, indexSize);
-
-            int size = convertedCount * 4;
-
-            if (autoBuffer != null)
-            {
-                DisposableBuffer buffer = autoBuffer.Get(cbs, 0, size);
-
-                return (buffer.Value, 0, MTLIndexType.UInt32);
-            }
-
-            return (new MTLBuffer(IntPtr.Zero), 0, MTLIndexType.UInt32);
-        }
-
-        private int GetIndexSize()
-        {
-            return _type switch
-            {
-                IndexType.UInt => 4,
-                IndexType.UShort => 2,
-                _ => 1,
-            };
-        }
-    }
-}