Add AsEventListener attribute

[HypeMC]

Similar to #1345 allows replacing configs such as:

App\EventListener\MyListener:
    tags:
        - { name: 'doctrine.event_listener', event: 'preFlush' }
        - { name: 'doctrine.event_listener', event: 'postFlush' }

with attributes:

use Doctrine\Bundle\DoctrineBundle\Attribute\AsEventListener;
use Doctrine\ORM\Events;

#[AsEventListener(Events::preFlush)]
#[AsEventListener(Events::postFlush)]
class MyListener
{
// ...
}

[ostrolucky]

thx!