Deprecate ContainerAwareEventDispatcher

Replaced the use of ContainerAwareEventDispatcher and changed existing updated type annotations to use Symfony\Component\EventDispatcher\EventDispatcherInterface instead of Symfony\Contracts\EventDispatcher\EventDispatcherInterface. That last change is more of a nitpick update because they are one and the same.

Thanks a lot, looks great and makes sense.
Merged.
Thanks again!