…ng property (FabienSalles)

This PR was merged into the 4.3 branch.

Discussion
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[Workflow] Fix error when we use ValueObject for the marking property

| Q             | A
| ------------- | ---
| Branch?       | 4.3
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Tickets       | Fix #28203 #22031
| License       | MIT

Fix Illegal offset type in `MethodMarkingStore` class when we use Value Object for
the marking property.

Now, we can avoid to use only a string an we can have a Subject class with a Value Object like this :
```php
final class State
{
    public const DRAFT = 'draft';
    public const REVIEWED = 'reviewed';
    public const REJECTED = 'rejected';
    public const PUBLISHED = 'published';

     /** @var string */
    private $state;

    public function __construct(string $state)
    {
        // some validation
        $this->state = $state;
    }

    public function __toString()
     {
         return $this->state;
    }

    public static function Draft()
     {
         return new self(self::DRAFT);
     }
    ...
}

final class Subject
{
    private $marking;

    public function __construct(State $marking = null)
    {
        $this->marking = $marking;
    }

    public function getMarking()
    {
        return $this->marking;
    }

    public function setMarking($marking)
    {
        $this->marking = $marking instanceof State ? $marking : new State($marking);
    }

```

Commits
-------

6570d5c Fix error when we use VO for the marking property