compiler/types: Use glsl_get_type_name() to access the type name

compiler/types: Use glsl_get_type_name() to access the type name

This will allow us later to store builtin names in a different way.

Reviewed-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25191>