`BindGroupLayoutEntry::count` Validation Does Not Check That Shader Uses Binding Arrays

[daxpedda]

When creating a BindGroupLayout, a BindGroupLayoutEntry::count can be specified to signify a binding array.
This is currently unchecked and will work transparently with a texture array, however it will still require Features::TEXTURE_BINDING_ARRAY.

This should probably throw an error, if used with a texture array, saying that it expects a binding array.

@cwfitzgerald as you pointed out on Matrix.