Fix 5.4 deprecs & types

[ogizanagi]

I think we should be safe for allowing Symfony 6 without major BC breaks, so we may just release a minor version.
The main impact is on DBAL types for which some types are added on methods, but these are not likely to be overwritten in the context, nor it'll be a big BC on userland.

If it comes to be an issue, we could still conditionally declare the classes according to the detected return types in base ones.

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refs:

• https://wouterj.nl/2021/09/symfony-6-native-typing
• https://symfony.com/doc/5.4/setup/upgrade_major.html#upgrading-to-symfony-6-add-native-return-types

[chalasr]

👍 for a minor