11.4.x system updates need to happen after entity usage config update

Actually I want to make the code a bit more robust and just ignore the old format. Just in case other updates cause the same problem

This is the first step to automating discovery of the site's url - now we've got all the internal checking happening in the new SiteDomain class. This means that we can then inject the RequestContext and use \Drupal\Core\Routing\RequestContext::getCompleteBaseUrl() to add that automatically. We can also add the public streamwrapper and automatically add that's external URL too. That would cover things like S3 storage where files are stored on a different URL.