nir: Vectorize intrinsics

nir: Vectorize intrinsics

We used to have the number of components built into the intrinsic.  This
meant that all of our load/store intrinsics had vec1, vec2, vec3, and vec4
variants.  This lead to piles of switch statements to generate the correct
intrinsic names, and introspection to figure out the number of components.
We can make things much nicer by allowing "vectorized" intrinsics.

Reviewed-by: Connor Abbott <cwabbott0@gmail.com>