`partProviders` was a `stateIn(WhileSubscribed)` flow, so its upstream
map ran again every time the clock widget was subscribed after the
launcher had been in the background - and built new part providers.
Providers cache what their ranking is based on, so the new agenda part
started at ranking 0, vanished while the launcher was gone and only came
back once its query had run again.
Build the provider list in `viewModelScope` into a `MutableStateFlow`
instead, so the instances (and their cached state) survive for as long
as the ViewModel does. Their ranking flows are still only collected
while the widget is subscribed, so observers are still registered and
unregistered with the widget's lifecycle.
Jonas Haugesen
c8109d9197