Purpose of this commit is to make ``get_access_action`` private as it is not
necessary to expose it directly. Website management is also made explicit
using a ``force_website`` parameter instead of relying on context key of the
same name. This allows to better understand the method code flow.
Contains also some code fix / improvements :
* Website forum: update code to better skip the frontend redirection if the
forum is not active and frontend is not forced;
* Website slides: respect force website parameter in redirection;
Task-2710804 (Mail: Clean Mail.Thread API)
Part-of: odoo/odoo#82167