nir: Add a array-of-vector variable shrinking pass

This pass looks for variables with vector or array-of-vector types and
narrows the type to only the components used.

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>

src/compiler/nir/nir.h

@@ -2659,6 +2659,7 @@ void nir_dump_cfg(nir_shader *shader, FILE *fp);
 
 int nir_gs_count_vertices(const nir_shader *shader);
 
+bool nir_shrink_vec_array_vars(nir_shader *shader, nir_variable_mode modes);
 bool nir_split_array_vars(nir_shader *shader, nir_variable_mode modes);
 bool nir_split_var_copies(nir_shader *shader);
 bool nir_split_per_member_structs(nir_shader *shader);