Move to new header API

[juliushaertl]

With the files to vue migration we will need to adapt the rich workspace area to the new API from nextcloud-libraries/nextcloud-files#717

The API is slightly different from the current and hands over the Folder object which we can then use to directly tell if we shall render rich workspace or not.

Additional dav property needs to be registered through: https://nextcloud-libraries.github.io/nextcloud-files/functions/registerDavProperty.html

This will also fill the missing gap of #4254

FYI @mejo- Since you worked on the above PR.