[2.2][Security] concurrent sessions

an implementation of the Spring concurrent sessions in the Security Component, now using Doctrine DBAL. Can be configured like:

    security:
        ...
        session_registry:
            connection: default
            tables:
                session_information: cs_session_information
    
        firewalls:
            ...
            secured_area:
                ...
                session_concurrency:
                    max_sessions: 5
                    expiration_url: /expired

to init, run the init:concurrent-session command, which will create a DBAL implementation of the Symfony\Component\Security\Http\Session\SessionRegistryStorageInterface. You can also provide a custom implementation.