Added (migrated) CustomNavigationHandler (which should partially fix the AvatarIcon in the NavBar in iOS)
Added (migrated) CustomContentPageHandler (which should mostly place the AvatarIcon in the navBar in the correct place for iOS)
Added Task.Delay (workaround) to allow the Avatar to load in iOS on the LoginPage
Added workaround for iOS bug with the toolbar size (more info in comment in AvatarImageSource.cs)
Went through the AccountViewCell MAUI-Migration comments. (and deleted/added more comments as needed)
Migrated some Device calls to DeviceInfo and MainThread
Added (migrated) CustomTabbedHandler (for managing the iOS TabBar)
