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/TextureBase.cs

@@ -1,67 +0,0 @@
-using Ryujinx.Graphics.GAL;
-using SharpMetal.Metal;
-using System;
-using System.Runtime.Versioning;
-using System.Threading;
-
-namespace Ryujinx.Graphics.Metal
-{
-    [SupportedOSPlatform("macos")]
-    abstract class TextureBase : IDisposable
-    {
-        private int _isValid = 1;
-
-        public bool Valid => Volatile.Read(ref _isValid) != 0;
-
-        protected readonly Pipeline Pipeline;
-        protected readonly MTLDevice Device;
-        protected readonly MetalRenderer Renderer;
-
-        protected MTLTexture MtlTexture;
-
-        public readonly TextureCreateInfo Info;
-        public int Width => Info.Width;
-        public int Height => Info.Height;
-        public int Depth => Info.Depth;
-
-        public MTLPixelFormat MtlFormat { get; protected set; }
-        public int FirstLayer { get; protected set; }
-        public int FirstLevel { get; protected set; }
-
-        public TextureBase(MTLDevice device, MetalRenderer renderer, Pipeline pipeline, TextureCreateInfo info)
-        {
-            Device = device;
-            Renderer = renderer;
-            Pipeline = pipeline;
-            Info = info;
-        }
-
-        public MTLTexture GetHandle()
-        {
-            if (_isValid == 0)
-            {
-                return new MTLTexture(IntPtr.Zero);
-            }
-
-            return MtlTexture;
-        }
-
-        public virtual void Release()
-        {
-            Dispose();
-        }
-
-        public void Dispose()
-        {
-            bool wasValid = Interlocked.Exchange(ref _isValid, 0) != 0;
-
-            if (wasValid)
-            {
-                if (MtlTexture != IntPtr.Zero)
-                {
-                    MtlTexture.Dispose();
-                }
-            }
-        }
-    }
-}