Remove uses of TransformComponent.ChildEntities (#22442)

* Make output of ChildEnumerator non-nullable

* Remove uses of ChildEntities

* poke tests

---------

Co-authored-by: metalgearsloth <comedian_vs_clown@hotmail.com>

Content.Server/NPC/Systems/NPCUtilitySystem.cs

@@ -454,7 +454,7 @@ public sealed class NPCUtilitySystem : EntitySystem
 
         while (enumerator.MoveNext(out var child))
         {
-            RecursiveAdd(child.Value, entities);
+            RecursiveAdd(child, entities);
         }
     }