I realized that it was not entirely fair to expect users to fetch a
scene's item list, then search the list on the client in order to find
an item ID, so this is a compromise. This will also help developers
move from the 4.x scene item functionality to 5.x's
Operating on scene items by relying on source name can be dangerous
and in some cases exhibit what would be considered undefinied behavior.
Operating on scene items using IDs is best practice.
