Fix remaining Symfony deprecations

[dunglas]

I figured out that many Symfony deprecations aren't fixed yet. They are just hidden by our default PHPUnit Bridge configuration.

To display these deprecations, you can run SYMFONY_DEPRECATIONS_HELPER=max[total]=0 vendor/bin/phpunit.

Pull Requests welcome!

[teohhanhui]

SYMFONY_DEPRECATIONS_HELPER=max[total]=0

We already use that in one of our Travis jobs, right?