ntt: Switch to new-style registers and modifiers

ntt: Switch to new-style registers and modifiers

Use all the nir_legacy.h features to transition away from the deprecated
structures. shader-db is quite happy. I assume that's a mix of more aggressive
source mod usage and better coalescing (nir-to-tgsi doesn't copyprop).

   total instructions in shared programs: 900179 -> 887156 (-1.45%)
   instructions in affected programs: 562077 -> 549054 (-2.32%)
   helped: 5198
   HURT: 470
   Instructions are helped.

   total temps in shared programs: 91165 -> 91162 (<.01%)
   temps in affected programs: 398 -> 395 (-0.75%)
   helped: 21
   HURT: 18
   Inconclusive result (value mean confidence interval includes 0).

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Tested-by: Pavel Ondračka <pavel.ondracka@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24116>