Fix EZP-22400: Use FOSHttpCacheBundle

> https://jira.ez.no/browse/EZP-22400

This PR adds support of FOSHttpCacheBundle and replaces eZ custom logic by FOSHttpCache

Depends on:
* https://github.com/FriendsOfSymfony/FOSHttpCache/pull/128 (merged)
* https://github.com/FriendsOfSymfony/FOSHttpCacheBundle/pull/152

## TODO
* [x] Implement HTTP cache invalidation
* [x] Make user hash use FOSHttpCache *User Context*
* [x] Tests
it is not equivalent in all cases:

- casting ``null`` to an array returns an empty array, not an array with ``null`` in it
- casting a Traversable object to an array traverses the iterator (like ``iterator_to_array``)

All other cases are indeed returning an array with the value as single element