[SymfonyCodeQuality] From listener to subscriber

[TomasVotruba]

Before

<?php

class SomeListener
{
     public function methodToBeCalled()
     {
     }
}

# config.yaml
services:
    SomeListener:
        tags:
            - { name: kernel.event_listener, event: 'some_event', method: 'methodToBeCalled' }

After

<?php

use Symfony\Component\EventDispatcher\EventSubscriberInterface;

class SomeEventSubscriber implements EventSubscriberInterface
{
     /**
      * @return mixed[]
      */
     public static function getSubscribedEvents(): array
     {
         return ['some_event' => 'methodToBeCalled'];  
     }

     public function methodToBeCalled()
     {
     }
}