Updated Issue Description:

Symfony/phpBB are not registering CLI services in extensions in some scenarios. It appears it may be related to directory permissions for the cache/production directory (see comment-64615)

Original Issue Description:

The CLI commands `cron:run` and `cron:list` do not appear to be aware of cron tasks within extensions. I've duplicated this on a fresh 3.3.1 install with a minimal extension created using the phpBB Skeleton Extension. As of 2021-05-24, this is still happening with phpBB 3.3.4.

The extension is https://github.com/gRegorLove/phpbb-extension-example and my original thread with some more details is https://www.phpbb.com/community/viewtopic.php?f=661&t=2565316

I found a similar bug was fixed previously: https://tracker.phpbb.com/browse/PHPBB3-12685