Expose APIs for clearing the ECMs internal state tracking addition and removal (backport #3002)

include/gz/sim/EntityComponentManager.hh

@@ -684,21 +684,19 @@ namespace gz
                   const std::string &_name) const;
 
       /// \brief Clear the list of newly added entities so that a call to
-      /// EachAdded after this will have no entities to iterate. This function
-      /// is protected to facilitate testing.
-      protected: void ClearNewlyCreatedEntities();
+      /// EachAdded after this will have no entities to iterate.
+      public: void ClearNewlyCreatedEntities();
 
       /// \brief Clear the list of removed components so that a call to
       /// RemoveComponent doesn't make the list grow indefinitely.
-      protected: void ClearRemovedComponents();
+      public: void ClearRemovedComponents();
 
       /// \brief Process all entity remove requests. This will remove
-      /// entities and their components. This function is protected to
-      /// facilitate testing.
-      protected: void ProcessRemoveEntityRequests();
+      /// entities and their components.
+      public: void ProcessRemoveEntityRequests();
 
       /// \brief Mark all components as not changed.
-      protected: void SetAllComponentsUnchanged();
+      public: void SetAllComponentsUnchanged();
 
       /// Compute the diff between this EntityComponentManager and _other at the
       /// entity level. This does not compute the diff between components of an