[Symfony] Make controllers explicitly public

Created by: Addvilz

Description

Yet another Symfony4 compatibility fix.

Since Symfony 3.4, services in container are private by default. Because of that, doing a resource import in root routing (for example, to prefix paths or do something similar) will not work, as the controllers are inaccessible, resulting in an error.

Suggest a fix/enhancement

The only backwards compatible fix is to mark these controller services public by default.

I will open a PR to address this issue.