Add a bulk create method to the queue implementations

To bike-shed here I would simply call it createItems or possibly createMultiple, similar to EntityInterface::loadMultiple.

I'm not sure what is the BC way of adding methods to an interface. We could create a new interface that extends QueueInterface and provide a trait that has a default implementation with a simple loop.

It looks like we could easily refactor \Drupal\Core\Queue\DatabaseQueue::doCreateItem to insert multiple items at once with a bit of massaging. In fact, the simple_sitemap module already does this in SimpleSitemapQueue. Not quite sure about the return value though.

At a glance the redis client already allows preprending multiple items, so redis module can easily make use of that too.

In core there are not a lot of places that could make use of this. I've identified the following:

• _batch_populate_queue - multiple batch operations
• locale_cron_fill_queue - same as above
• \Drupal\media\Entity\Media::postSave - download thumbnails for multiple translations

So we're probably only saving a handful of queries there. But there are more places in contrib that could also make use of this. A few I see in the project I'm currently working on:

• entity_reference_revisions_entity_delete
• \Drupal\linkchecker\LinkCheckerService::queueLinks
• \Drupal\workbench_email\EventSubscriber\WorkbenchTransitionEventSubscriber::onContentModerationTransition

I'm not sure that system.module is the right component though, so changing to base system.