zink: Rework sparse texture lowering

Instead of the previous fragile attempt to handle sparse_resident_and by crawling deref chains, we now insert an is_sparse_resident_zink intrinsic immediately after the tex or sparse_load intrinsic and define Zink's sparse resident codes to always be 0/1. Then sparse_resident_and becomes iand and is_sparse_texels_resident becomes != 0 and everything is well-defined and robust.