Implemented EZP-19411: Avoid file_exists and include calls for register...

...ing datatypes and workflows

This is related to the big change added in https://github.com/ezsystems/ezpublish-legacy/commit/a6bfaa622342b728951c7f45bb066828440c3be3 

The goal is adapt extensions  to this new possibility. I will add PRS for other extensions and finally i will update the jira related issue