Allow using a queue to dispatch EntityEvents::ENTITY_ACTION instead of at the end of each request

[mglaman]

Slack link to convo https://drupal.slack.com/archives/C1AKSFBEW/p1676316211242009

I'm concerned on the scalability and performance if a Drupal site pushed requests to 5-10 or more Next.js sites. Drupal makes a blocking request to the Next.js API endpoint. That API endpoint calls await response.revalidate(slug) before responding.

My concern is how long does await response.revalidate(slug) take while blocking the response to Drupal? Guzzle does support async requests, but reactions to EntityEvents::ENTITY_ACTION are not processed at once but individually. So we cannot batch async them.

Moving to a queue would allow for greater scalability when there are more Next.js sites receiving content entity changes.