Better support for Derivative queue workers

Not sure what I was looking at, but the item count for subqueues looks fine in fact.

Here's the deriver i'm using for the curious:

/**
 * @file
 * Contains \Drupal\media_analysis\Plugin\Derivative.
 */

namespace Drupal\media_analysis\Plugin\Derivative;

use Drupal\Component\Plugin\Derivative\DeriverBase;
use Drupal\Core\Entity\EntityStorageInterface;
use Drupal\Core\Plugin\Discovery\ContainerDeriverInterface;
use Drupal\media_analysis\HookImplementations;
use Symfony\Component\DependencyInjection\ContainerInterface;

/**
 * Provides block plugin definitions for nodes.
 *
 * @see \Drupal\media_analysis\Plugin\QueueWorker\MediaAnalysisWorker
 */
class MediaAnalysisWorker extends DeriverBase implements ContainerDeriverInterface {

  /**
   * Constructor.
   *
   * @param \Drupal\Core\Entity\EntityStorageInterface $node_storage
   *   The node storage.
   */
  public function __construct(private readonly EntityStorageInterface $nodeStorage) {
  }

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container, $base_plugin_id) {
    return new static(
      $container->get('entity_type.manager')->getStorage('node')
    );
  }

  /**
   * {@inheritdoc}
   */
  public function getDerivativeDefinitions($base_plugin_definition) {
    $nodes = $this->nodeStorage->loadByProperties(['type' => 'media_channel']);
    foreach ($nodes as $node) {
      $this->derivatives[$node->id()] = $base_plugin_definition;
      $this->derivatives[$node->id()]['admin_label'] = t('Channel: ') . $node->label();
    }
    return $this->derivatives;
  }

}

This deriver then gets referenced in the @Cron annotation field of my existing cron queue worker:

/**
 * Defines 'media_analysis' queue worker.
 *
 * @QueueWorker(
 *   id = "media_analysis",
 *   title = @Translation("Media Analysis: Channels"),
 *   cron = {"time" = 60},
 *   deriver = "\Drupal\media_analysis\Plugin\Derivative\MediaAnalysisWorker"
 * )
 */

And I have another procedure to insert queue items with a queue name like media_analysis:$nid which then get processed by the queue worker, thanks to Derivative API.

The derivative is mostly useful so that I can more easily prevent duplicate queue items, but it breaks the Queue UI pretty badly.

I started looking at adapting Queue UI, but it's a bit of a can of worms - will require special handling for every route and callback that uses the {queueName} placeholder, for starters.
So IMO it's fine to leave this issue on Postponed, and I'll implement a custom UI for my special case.