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/BlitMs.metal

@@ -1,45 +0,0 @@
-#include <metal_stdlib>
-
-using namespace metal;
-
-struct CopyVertexOut {
-    float4 position [[position]];
-    float2 uv;
-};
-
-struct TexCoords {
-    float data[4];
-};
-
-struct ConstantBuffers {
-    constant TexCoords* tex_coord;
-};
-
-struct Textures
-{
-    texture2d_ms<FORMAT, access::read> texture;
-};
-
-vertex CopyVertexOut vertexMain(uint vid [[vertex_id]],
-                                constant ConstantBuffers &constant_buffers [[buffer(CONSTANT_BUFFERS_INDEX)]]) {
-    CopyVertexOut out;
-
-    int low = vid & 1;
-    int high = vid >> 1;
-    out.uv.x = constant_buffers.tex_coord->data[low];
-    out.uv.y = constant_buffers.tex_coord->data[2 + high];
-    out.position.x = (float(low) - 0.5f) * 2.0f;
-    out.position.y = (float(high) - 0.5f) * 2.0f;
-    out.position.z = 0.0f;
-    out.position.w = 1.0f;
-
-    return out;
-}
-
-fragment FORMAT4 fragmentMain(CopyVertexOut in [[stage_in]],
-                             constant Textures &textures [[buffer(TEXTURES_INDEX)]],
-                             uint sample_id [[sample_id]]) {
-    uint2 tex_size = uint2(textures.texture.get_width(), textures.texture.get_height());
-    uint2 tex_coord = uint2(in.uv * float2(tex_size));
-    return textures.texture.read(tex_coord, sample_id);
-}