Bug 211303

Summary:
WebGPU: copyTextureToTexture() has an implementation bug (src copy view info is used also as dst).

See:
GPUCommandBufferMetal.mm#214,217

[blitEncoder()
        copyFromTexture:src.texture->platformTexture()
        sourceSlice:src.arrayLayer
        sourceLevel:src.mipLevel
        sourceOrigin:MTLOriginMake(src.origin.x, src.origin.y, src.origin.z)
        sourceSize:MTLSizeMake(size.width, size.height, size.depth)
        toTexture:dst.texture->platformTexture()
        destinationSlice:src.arrayLayer
        destinationLevel:src.mipLevel
        destinationOrigin:MTLOriginMake(dst.origin.x, dst.origin.y, dst.origin.z)];

In particular:
        destinationSlice:src.arrayLayer
        destinationLevel:src.mipLevel

Should be:
        destinationSlice:dst.arrayLayer
        destinationLevel:dst.mipLevel