radv/rt: use stage ID as handle for general and closestHit shaders
This avoids some code duplication and divergence. Quake II RTX: Totals from 7 (0.01% of 134913) affected shaders: CodeSize: 218880 -> 217592 (-0.59%) Instrs: 39692 -> 39468 (-0.56%) Latency: 789091 -> 761581 (-3.49%) InvThroughput: 526061 -> 507721 (-3.49%) VClause: 1202 -> 1188 (-1.16%) Copies: 4649 -> 4621 (-0.60%) Branches: 1605 -> 1598 (-0.44%) Reviewed-by:Konstantin Seurer <konstantin.seurer@gmail.com> Part-of: <mesa/mesa!17301>