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/Shuttles/Systems/ShuttleSystem.GridFill.cs

@@ -148,7 +148,7 @@ public sealed partial class ShuttleSystem
             if (!dockQuery.TryGetComponent(child, out var dock))
                 continue;
 
-            return (child.Value, dock);
+            return (child, dock);
         }
 
         return null;