Change Instantiator to Repeater in NavigationTabBar
The Instantiator was causing issues, since NavigationTabButtons that were supposed to be destroyed weren't really destroyed and still showed up as buttons in the tabGroup. This was causing infinite loops in several apps under certain circumstances (plasma dialer, koko, discover, kclock, kasts, tokodon).
Additionally, change the associated test to be sensitive to the original issue. This is done by using a binding on the checked property of one of the buttons.
Edited by Bart De Vries