Move 'webfiles' security domain to federated security domain below /webfiles and cms users should have read access to webfiles

Currently in 14.0.0-securitydomain-SNAPSHOT, authors and editors do not have read access to /webfiles. However, for 'switch template' feature (select different FTL for a component in channel mgr) they need read access.

Currently, the webfiles are only readable for users with role

xm-hst-webfiles-reader

However, also cms users should be able to read them. Next to that, '/webfiles' is bootstrapped by hippo-services-webfiles and has namespace prefix webfiles:webfiles : Hence, the domain security should be decoupled from the HST code, and the userrole should be something like xm_webfiles_reader and should not include any 'hst' part in the name: 'webfiles' is an upstream project wrt the HST