[Csrf] component fixes
minor #9311 [Csrf] component fixes (Tobion)

This PR was squashed before being merged into the master branch (closes #9311).

Discussion
----------

[Csrf] component fixes

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #9216
| License       | MIT
| Doc PR        | -

- [Csrf] fixed some phpdocs
- [Csrf] fixed return types (also https://github.com/symfony/symfony/pull/9216#discussion_r6797190 )
- [Csrf] fixed test class namespaces

Commits
-------

d7eb8ff [Csrf] component fixes