FastImmediateObserver<T>
Specialized scheduled observer similar to a scheduled observer for the immediate scheduler.
            
                
Creates a new scheduled observer that proxies to the specified observer.
            
Disposes the observer.
            
Notifies the observer of pending work. This will either cause the current owner to
            process the newly enqueued notifications, or it will cause the calling thread to
            become the owner and start processing the notification queue.
            
Notifies the observer of pending work. This will either cause the current owner to
            process the newly enqueued notifications, or it will cause the calling thread to
            become the owner and start processing the notification queue.
            
Enqueues an OnCompleted notification.
            
Enqueues an OnError notification.
            
Enqueues an OnNext notification.