glsl: Move lower_vector_insert to GLSL-to-NIR.

We already have a nir_builder equivalent for generating this code, just
use that instead of doing it in GLSL.

No change on r300 shader-db.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21476>

src/compiler/glsl/meson.build

@@ -213,7 +213,6 @@ files_libglsl = files(
   'lower_tess_level.cpp',
   'lower_vec_index_to_cond_assign.cpp',
   'lower_vector_derefs.cpp',
-  'lower_vector_insert.cpp',
   'opt_algebraic.cpp',
   'opt_constant_folding.cpp',
   'opt_constant_propagation.cpp',