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.
> It's certainly something to think about. For example, we use relation list for building menus quite often. Those node IDs were important to properly reference to menu items.

not the tool for the job ;)

> But we digress :)

yes, topic for next summercamp :)