Allow packages from "symfony/*" ^7

[phansys]

Subject

I am targeting this branch, because these changes respect BC.

Supersedes #2425.

Changelog

### Added
- Support for packages from `symfony/*` 7.x

To do

• Use a stable constraint for sonata-project/classification-bundle.

[VincentLanglet]

This is a BC break for non SF 7 users.

We should use something like
https://github.com/sonata-project/SonataAdminBundle/blob/4.x/src/ArgumentResolver/CompatibleValueResolverInterface.php

if (interface_exists(MessageHandlerInterface::class)) {
    /** @internal */
    interface CompatibleMessageHandlerInterface extends MessageHandlerInterface
    {
    }
} else {
    /** @internal */
    interface CompatibleMessageHandlerInterface
    {
    }
}

and use it here:

final class GenerateThumbnailsHandler implements CompatibleMessageHandlerInterface