…num as parameters (ogizanagi)

This PR was squashed before being merged into the 4.4 branch.

Discussion
----------

[DependencyInjection][FrameworkBundle] Fix using PHP 8.1 enum as parameters

| Q             | A
| ------------- | ---
| Branch?       | 4.4 <!-- see below -->
| Bug fix?      | yesish
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tickets       | Fix #44834  <!-- prefix each issue number with "Fix #", no need to create an issue if none exist, explain below instead -->
| License       | MIT
| Doc PR        | N/A

While #40857 allowed using enums in DI, it does not allow using these in parameters.

This would be the actual fix for #44834, which shows the error you'll get trying to use enum as DI parameters (appart from the binding issue fixed in #44838):

![image](https://user-images.githubusercontent.com/2211145/147762495-f57f1fff-f56a-4e87-bbc4-3bba97a8e81b.png)

given:

```php
namespace App;

enum Status {
    case Draft;
    case Deleted;
    case Published;
}
```

```yaml
# services.yaml
parameters:
    default_status: !php/const App\Status::Draft
```

The exception happens because the `PhpDumper` misses the leading slash:

```diff

    protected function getDefaultParameters(): array
    {
        return [
-            'default_status' => App\Status::Draft,
+            'default_status' => \App\Status::Draft,
        ];
    }
```

While this would fix using enums as DI parameters as of Symfony < 6,
the `ParameterBagInterface::get/set` and `ContainerInterface::setParameter/getParameter` are not allowing `\UnitEnum` and adding these in phpdoc is an issue since actual typehints and return types were added as of Symfony 6.
=> So this PR is a BC break, but hopefully nobody will be hit by it 🤞🏻

(poke `@ismail1432` -
https://twitter.com/SmaineDev/status/1476237072826613763?s=20)

Commits
-------

ac36617 [DependencyInjection][FrameworkBundle] Fix using PHP 8.1 enum as parameters