Preserve live lane predicates through RDNA2 whole-quad expansion
Keep the source-live predicate when WQM expands a scalar mask, so entry masks remain known live without an instruction pre-scan. Preserve scalar mask values, SCC, half writes, and raw-source behavior.
Cover entry pixel masks, cross-half copies, and scalar/high-word sources with existing shader regression suites.
Co-authored-by: nmzik <Nmzik@mail.ru>
Co-authored-by: Douglas <douglasproducoes21@gmail.com>
