Change API for PdmObjectHandle and PdmFieldHandle

* Refactor interface to PdmObjectHandle and PdmFieldHandle
Return objects instead of passing in structures as parameters

* Add nodiscard to several functions
* Remove redundant this->
* Rename to ptrReferencedObjectsByType

ApplicationLibCode/Commands/RicDeleteSubItemsFeature.cpp

@@ -223,8 +223,7 @@ void RicDeleteSubItemsFeature::deleteSubItems( bool onlyDeleteUnchecked )
 
                 collection->updateConnectedEditors();
 
-                RimProject* proj = nullptr;
-                collection->firstAncestorOrThisOfType( proj );
+                RimProject* proj = RimProject::current();
                 if ( proj ) proj->reloadCompletionTypeResultsInAllViews();
             }
         }