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/Shaders/ConvertIndexBuffer.metal

@@ -1,59 +0,0 @@
-#include <metal_stdlib>
-
-using namespace metal;
-
-struct IndexBufferPattern {
-    int pattern[8];
-    int primitiveVertices;
-    int primitiveVerticesOut;
-    int indexSize;
-    int indexSizeOut;
-    int baseIndex;
-    int indexStride;
-    int srcOffset;
-    int totalPrimitives;
-};
-
-struct InData {
-    uint8_t data[1];
-};
-
-struct OutData {
-    uint8_t data[1];
-};
-
-struct StorageBuffers {
-    device InData* in_data;
-    device OutData* out_data;
-    constant IndexBufferPattern* index_buffer_pattern;
-};
-
-kernel void kernelMain(device StorageBuffers &storage_buffers [[buffer(STORAGE_BUFFERS_INDEX)]],
-                       uint3 thread_position_in_grid [[thread_position_in_grid]])
-{
-    int primitiveIndex = int(thread_position_in_grid.x);
-    if (primitiveIndex >= storage_buffers.index_buffer_pattern->totalPrimitives)
-    {
-        return;
-    }
-
-    int inOffset = primitiveIndex * storage_buffers.index_buffer_pattern->indexStride;
-    int outOffset = primitiveIndex * storage_buffers.index_buffer_pattern->primitiveVerticesOut;
-
-    for (int i = 0; i < storage_buffers.index_buffer_pattern->primitiveVerticesOut; i++)
-    {
-        int j;
-        int io = max(0, inOffset + storage_buffers.index_buffer_pattern->baseIndex + storage_buffers.index_buffer_pattern->pattern[i]) * storage_buffers.index_buffer_pattern->indexSize;
-        int oo = (outOffset + i) * storage_buffers.index_buffer_pattern->indexSizeOut;
-
-        for (j = 0; j < storage_buffers.index_buffer_pattern->indexSize; j++)
-        {
-            storage_buffers.out_data->data[oo + j] = storage_buffers.in_data->data[storage_buffers.index_buffer_pattern->srcOffset + io + j];
-        }
-
-        for(; j < storage_buffers.index_buffer_pattern->indexSizeOut; j++)
-        {
-            storage_buffers.out_data->data[oo + j] = uint8_t(0);
-        }
-    }
-}