when a file indexer has finished use its imported tracks count for notifications
start to tune initial music discovery to be faster to show something to the user
small optimisations in the music models to tune for performance
optimize music discovery by moving MusicListenersManager and the models to c++
we are now creating MusicListenersManager and the models in pure c++
including the connections of signal/slots to update the models
this feels much faster than when this was done in qml
tune the busy indicator to only show up when really needed