Implementing the option to use multiple LifetimeSupervisors

[alexandrejh]

Feature: Allowing multiple LifetimeSupervisors with different behaviors
I need to use two different LifetimeSupervisor, one with CountBasedLifetimeSupervisor and other with TimeAndCountBasedLifetimeSupervisor. If I create 2 separated Notifiers the notifications can be displayed over the notifications that are already opened.
For this I create a way to set multiple LifetimeSupervisors to same Notifiers and same DisplaySupervisor.
To work correctly the LifetimeSupervisors need to be cached, to pass the same instance.
Example of how to use:

private static Notifier GenerateNotifier(double notificationLifeTime, Corner notificationPosition)
{
    //here I check if the LifetimeSupervisor to use is based on time
    //if it is null I create new instance
    if (notificationLifeTime > 0 && _lifetimeTimeAndCount == null)
    {
        _lifetimeTimeAndCount = new TimeAndCountBasedLifetimeSupervisor(
            notificationLifetime: TimeSpan.FromSeconds(notificationLifeTime),
            maximumNotificationCount: MaximumNotificationCount.FromCount(5));
    }
    
    //here I check if the LifetimeSupervisor to use is based only on count
    //if it is null I create new instance
    if (notificationLifeTime == 0 && _lifetimeCount == null)
    {
        _lifetimeCount = new CountBasedLifetimeSupervisor(maximumNotificationCount: MaximumNotificationCount.FromCount(5));
    }

    //get the correct LifetimeSupervisor to use
    INotificationsLifetimeSupervisor lifetimeSupervisor = notificationLifeTime > 0 ? (INotificationsLifetimeSupervisor)_lifetimeTimeAndCount : (INotificationsLifetimeSupervisor)_lifetimeCount;

    if (_notifier == null)
    {
        _notifier = new Notifier(cfg =>
        {
            cfg.PositionProvider = new WindowPositionProvider(
                parentWindow: Application.Current.MainWindow,
                corner: notificationPosition,
                offsetX: 10,
                offsetY: 49);

            cfg.LifetimeSupervisor = lifetimeSupervisor;

            cfg.Dispatcher = Application.Current.Dispatcher;
        });
    }

    //update the current LifetimeSupervisor in the notifier
    _notifier.UpdateLifetimeSupervisor(lifetimeSupervisor);

    return _notifier;
}

In this case I'm not checking if the notificationLifeTime is different, but if you need you can cache into a dictionary with notificationLifeTime as the key.