[6.x] Add Macroable trait to the Dispatcher

[timrspratt]

The reason behind this, is I've recently needed a way of getting all events. Rather than extending the register my own Dispatcher in place of the Illuminate one, I think this would be a cleaner approach.

[GrahamCampbell]

Why do you specifically need the methods to be on this class?

[timrspratt]

@GrahamCampbell I'm currently doing the following to get all events that are of a certain type (where the listener event is of a class):

class Dispatcher extends \Illuminate\Events\Dispatcher
{
    public function getManagedEvents(): Collection
    {
        return collect($this->listeners)->filter(static function ($_, $event) {
            return is_subclass_of($event, ManagedEvent::class);
        });
    }
}

I thought making the Dispatcher extendible will allow other developers to be flexible, but another option would be to modify getListeners (or create a new public method), so that it can accept a closure as well as the event name.

public function getListeners($eventName)
{
    if (is_callable($eventName)) {
        $listeners = array_filter($this->listeners, $eventName);
    } else {
        $listeners = $this->listeners[$eventName] ?? [];
    }

    ...
}

My concern with the second solution is that the wildcard and interface listeners may pollute the list once filtered, for what I need anyway. Essentially I need a way of getting all events that are registered in the dispatcher that extend a specific class.