Edit mode normalize fails to respect locked groups

Add BKE_object_defgroup_flip_map_unlocked which excludes locked groups
from the flip-map.

Reviewed By: zanqdo, campbellbarton

Maniphest Tasks: T96787

Ref D15317

source/blender/blenkernel/intern/deform.c

@@ -589,7 +589,7 @@ static int *object_defgroup_unlocked_flip_map_ex(const Object *ob,
   int i, flip_num;
   int *map = MEM_mallocN(defbase_tot * sizeof(int), __func__);
 
-  for (int i = 0; i < defbase_tot; i++) {
+  for (i = 0; i < defbase_tot; i++) {
     map[i] = -1;
   }