nir: Drop nir_dest

Instead, we replace every use of it with nir_def.  Most of this commit
was generated by sed:

   sed -i -e 's/dest.ssa/def/g' src/**/*.h src/**/*.c src/**/*.cpp

A few manual fixups were required in lima and the nir_legacy code.

Acked-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24674>

src/asahi/compiler/agx_compiler.h

@@ -474,7 +474,7 @@ agx_vec_for_def(agx_context *ctx, nir_def *def)
 static inline agx_index
 agx_vec_for_intr(agx_context *ctx, nir_intrinsic_instr *instr)
 {
-   return agx_vec_for_def(ctx, &instr->dest.ssa);
+   return agx_vec_for_def(ctx, &instr->def);
 }
 
 static inline unsigned