I want to make an app that has a navigationsplitview with three columns on iPad but a tapbar on iPhone and small iPad windows. How should I do that? Since iOS 18 you can use tabview to make a tabbar on iPhone and a sidebar on iPad, but then you just have two columns. Is there a way to make this possible? Can you make a navigationsplitview sidebar move into a tabbar? And how did you do it before iOS 18 like in the podcasts app?