[Routing] Add the possibility to define a prefix for all routes of a controller

[javiereguiluz]

See symfony/symfony#24031 and https://symfony.com/blog/new-in-symfony-3-4-prefix-all-controller-route-names

[ismail1432]

I make a PR #9159 but I am not sure of the :

• content
• place in documentation

[javiereguiluz]

Fixed by #9186.