Rework tray icon activation behavior yet again

Rework tray icon activation behavior yet again

Finally figured out how to filter out double activation signals from QSystemTrayIcon.
Additionally, main window toggling is now controlled by the systray notification backends
rather than the tray itself. This ensures that we don't get a race condition where the
notification wants to activate the window, and the tray wants to hide it.

Consequently removing the crude inhibitActivation hack.