Fix phpcs issues in 2.2.x

I'd prefer to keep the autowired service and use another mechanism to add it, e.g. extending ServiceProviderBase to add the service if the Migrate module is installed.

I commented out the MigrateHooks class in metatag.services.yml and tried this:

namespace Drupal\metatag;

use Drupal\Core\DependencyInjection\ContainerBuilder;
use Drupal\Core\DependencyInjection\ServiceProviderBase;
use Symfony\Component\DependencyInjection\Definition;
use Symfony\Component\DependencyInjection\Reference;

/**
 * Service Provider for Metatag.
 */
class MetatagServiceProvider extends ServiceProviderBase {

  /**
   * {@inheritdoc}
   */
  public function register(ContainerBuilder $container) {
    $modules = $container->getParameter('container.modules');

    // If the Migrate module is installed, add the 
    if (isset($modules['migrate']) ) {
      // Add a service
      $service_definition = new Definition('Drupal\metatag\Hook\MigrateHooks');
      $service_definition->setClass('Drupal\metatag\Hook\MigrateHooks');
      $service_definition->setAutowired(TRUE);
      $container->setDefinition('Drupal\metatag\Hook\MigrateHooks', $service_definition);
    }
  }

}

With that change it then gives the following error:

Symfony\Component\DependencyInjection\Exception\RuntimeException: Cannot autowire service "Drupal\metatag\Hook\OutputHooks": argument "$metatagManager" of method "__construct()" references class "Drupal\metatag\MetatagManager" but no such service exists. You should maybe alias this class to the existing "metatag.manager" service.

That doesn't make sense to me?

I think #3620074: Move migration logic into submodule will take care of my concerns.

I created a clean MR using the two original commits, let's see if it works this time.

Committed. Thank you!