Fix EZP-22735: Make {{ path( 'ez_urlalias' ) }} polymorphic

A fix for already existing issue at JIRA: https://jira.ez.no/browse/EZP-22735

Common usecase is to generate an URL to content in Relation field value.
CS. Should be:

```php
if ( 
    isset( $parameters['content'] )
    && !$parameters['content'] instanceof Content 
    && !$parameters['content'] instanceof ContentInfo
)
{
    // ...
}
```