spirv: Add a warning for ArrayStride on arrays of blocks

spirv: Add a warning for ArrayStride on arrays of blocks

It's disallowed according to the SPIR-V spec or at least I think that's
what the spec says.  It's in a section explicitly about explicit layout
of things in the StorageBuffer, Uniform, and PushConstant storage
classes so it's not 100% clear that it applies with other storage
classes.  However, it seems like it should apply in general and
violating it can trigger (fairly harmless) asserts in NIR.

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>