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/DepthStencilCache.cs

@@ -1,68 +0,0 @@
-using Ryujinx.Graphics.Metal.State;
-using SharpMetal.Metal;
-using System.Runtime.Versioning;
-
-namespace Ryujinx.Graphics.Metal
-{
-    [SupportedOSPlatform("macos")]
-    class DepthStencilCache : StateCache<MTLDepthStencilState, DepthStencilUid, DepthStencilUid>
-    {
-        private readonly MTLDevice _device;
-
-        public DepthStencilCache(MTLDevice device)
-        {
-            _device = device;
-        }
-
-        protected override DepthStencilUid GetHash(DepthStencilUid descriptor)
-        {
-            return descriptor;
-        }
-
-        protected override MTLDepthStencilState CreateValue(DepthStencilUid descriptor)
-        {
-            // Create descriptors
-
-            ref StencilUid frontUid = ref descriptor.FrontFace;
-
-            using MTLStencilDescriptor frontFaceStencil = new()
-            {
-                StencilFailureOperation = frontUid.StencilFailureOperation,
-                DepthFailureOperation = frontUid.DepthFailureOperation,
-                DepthStencilPassOperation = frontUid.DepthStencilPassOperation,
-                StencilCompareFunction = frontUid.StencilCompareFunction,
-                ReadMask = frontUid.ReadMask,
-                WriteMask = frontUid.WriteMask
-            };
-
-            ref StencilUid backUid = ref descriptor.BackFace;
-
-            using MTLStencilDescriptor backFaceStencil = new()
-            {
-                StencilFailureOperation = backUid.StencilFailureOperation,
-                DepthFailureOperation = backUid.DepthFailureOperation,
-                DepthStencilPassOperation = backUid.DepthStencilPassOperation,
-                StencilCompareFunction = backUid.StencilCompareFunction,
-                ReadMask = backUid.ReadMask,
-                WriteMask = backUid.WriteMask
-            };
-
-            MTLDepthStencilDescriptor mtlDescriptor = new()
-            {
-                DepthCompareFunction = descriptor.DepthCompareFunction,
-                DepthWriteEnabled = descriptor.DepthWriteEnabled
-            };
-
-            if (descriptor.StencilTestEnabled)
-            {
-                mtlDescriptor.BackFaceStencil = backFaceStencil;
-                mtlDescriptor.FrontFaceStencil = frontFaceStencil;
-            }
-
-            using (mtlDescriptor)
-            {
-                return _device.NewDepthStencilState(mtlDescriptor);
-            }
-        }
-    }
-}