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/ImageArray.cs

@@ -1,74 +0,0 @@
-using Ryujinx.Graphics.GAL;
-using System.Runtime.Versioning;
-
-namespace Ryujinx.Graphics.Metal
-{
-    [SupportedOSPlatform("macos")]
-    internal class ImageArray : IImageArray
-    {
-        private readonly TextureRef[] _textureRefs;
-        private readonly TextureBuffer[] _bufferTextureRefs;
-
-        private readonly bool _isBuffer;
-        private readonly Pipeline _pipeline;
-
-        public ImageArray(int size, bool isBuffer, Pipeline pipeline)
-        {
-            if (isBuffer)
-            {
-                _bufferTextureRefs = new TextureBuffer[size];
-            }
-            else
-            {
-                _textureRefs = new TextureRef[size];
-            }
-
-            _isBuffer = isBuffer;
-            _pipeline = pipeline;
-        }
-
-        public void SetImages(int index, ITexture[] images)
-        {
-            for (int i = 0; i < images.Length; i++)
-            {
-                ITexture image = images[i];
-
-                if (image is TextureBuffer textureBuffer)
-                {
-                    _bufferTextureRefs[index + i] = textureBuffer;
-                }
-                else if (image is Texture texture)
-                {
-                    _textureRefs[index + i].Storage = texture;
-                }
-                else if (!_isBuffer)
-                {
-                    _textureRefs[index + i].Storage = null;
-                }
-                else
-                {
-                    _bufferTextureRefs[index + i] = null;
-                }
-            }
-
-            SetDirty();
-        }
-
-        public TextureRef[] GetTextureRefs()
-        {
-            return _textureRefs;
-        }
-
-        public TextureBuffer[] GetBufferTextureRefs()
-        {
-            return _bufferTextureRefs;
-        }
-
-        private void SetDirty()
-        {
-            _pipeline.DirtyImages();
-        }
-
-        public void Dispose() { }
-    }
-}