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/HashTableSlim.cs

@@ -1,143 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Runtime.CompilerServices;
-
-namespace Ryujinx.Graphics.Metal
-{
-    interface IRefEquatable<T>
-    {
-        bool Equals(ref T other);
-    }
-
-    class HashTableSlim<TKey, TValue> where TKey : IRefEquatable<TKey>
-    {
-        private const int TotalBuckets = 16; // Must be power of 2
-        private const int TotalBucketsMask = TotalBuckets - 1;
-
-        private struct Entry
-        {
-            public int Hash;
-            public TKey Key;
-            public TValue Value;
-        }
-
-        private struct Bucket
-        {
-            public int Length;
-            public Entry[] Entries;
-
-            [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            public readonly Span<Entry> AsSpan()
-            {
-                return Entries == null ? Span<Entry>.Empty : Entries.AsSpan(0, Length);
-            }
-        }
-
-        private readonly Bucket[] _hashTable = new Bucket[TotalBuckets];
-
-        public IEnumerable<TKey> Keys
-        {
-            get
-            {
-                foreach (Bucket bucket in _hashTable)
-                {
-                    for (int i = 0; i < bucket.Length; i++)
-                    {
-                        yield return bucket.Entries[i].Key;
-                    }
-                }
-            }
-        }
-
-        public IEnumerable<TValue> Values
-        {
-            get
-            {
-                foreach (Bucket bucket in _hashTable)
-                {
-                    for (int i = 0; i < bucket.Length; i++)
-                    {
-                        yield return bucket.Entries[i].Value;
-                    }
-                }
-            }
-        }
-
-        public void Add(ref TKey key, TValue value)
-        {
-            Entry entry = new()
-            {
-                Hash = key.GetHashCode(),
-                Key = key,
-                Value = value,
-            };
-
-            int hashCode = key.GetHashCode();
-            int bucketIndex = hashCode & TotalBucketsMask;
-
-            ref Bucket bucket = ref _hashTable[bucketIndex];
-            if (bucket.Entries != null)
-            {
-                int index = bucket.Length;
-
-                if (index >= bucket.Entries.Length)
-                {
-                    Array.Resize(ref bucket.Entries, index + 1);
-                }
-
-                bucket.Entries[index] = entry;
-            }
-            else
-            {
-                bucket.Entries =
-                [
-                    entry
-                ];
-            }
-
-            bucket.Length++;
-        }
-
-        public bool Remove(ref TKey key)
-        {
-            int hashCode = key.GetHashCode();
-
-            ref Bucket bucket = ref _hashTable[hashCode & TotalBucketsMask];
-            Span<Entry> entries = bucket.AsSpan();
-            for (int i = 0; i < entries.Length; i++)
-            {
-                ref Entry entry = ref entries[i];
-
-                if (entry.Hash == hashCode && entry.Key.Equals(ref key))
-                {
-                    entries[(i + 1)..].CopyTo(entries[i..]);
-                    bucket.Length--;
-
-                    return true;
-                }
-            }
-
-            return false;
-        }
-
-        public bool TryGetValue(ref TKey key, out TValue value)
-        {
-            int hashCode = key.GetHashCode();
-
-            Span<Entry> entries = _hashTable[hashCode & TotalBucketsMask].AsSpan();
-            for (int i = 0; i < entries.Length; i++)
-            {
-                ref Entry entry = ref entries[i];
-
-                if (entry.Hash == hashCode && entry.Key.Equals(ref key))
-                {
-                    value = entry.Value;
-                    return true;
-                }
-            }
-
-            value = default;
-            return false;
-        }
-    }
-}