glsl: Delete the vectorization opt pass.

glsl: Delete the vectorization opt pass.

Nothing uses it, and i965 was the last thing to.  Even if I enable it for
softpipe or crocus, it quickly causes NIR validation failures in shader-db
from swizzles outside the bounds of vectors.  Retire it in favor of
nir_opt_vectorize().

Reviewed-by: Alyssa Rosenzweig <alyssa@collabora.com>.
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14249>