Remove LayoutAwarePage, SuspensionManager, and other suspend-resume handling code. SuspensionManager::SaveAsync and related methods weren't actually called anywhere. I didn't attempt to remove the serialize/deserialize code at the ViewModel layer, although much of that is likely not needed either.
We may decide we want to persist more state through a suspend-terminate-resume cycle (as the app might have done a long time ago). But if we decide we want that, we should not use a persistence mechanism that's closely coupled to frame navigation.
