Wrong proxy class generation with default values as constants referncing `self`

Recent fix for constants in default parameter values broke proxy generation when constant is referenced as `self`.

Example entity code:
```
public function hasAccess(int $level = self::LEVEL_WORKER): bool
{
return $this->level >= $level;
}
```

Generated proxy class:
```
public function hasAccess(int $level = \self::LEVEL_WORKER): bool
{

$this->__initializer__ && $this->__initializer__->__invoke($this, 'hasAccess', [$level]);

return parent::hasAccess($level);
}

```

Which in effect causes Fatal Error in PHP 8.1:
```
[27-Sep-2022 09:11:12 UTC] PHP Fatal error: '\self' is an invalid class name in /app/var/cache/beta/doctrine/orm/Proxies/__CG__AppEntitySomeEntity.php on line 242
```