This removes the edit_folder_permission checks from the code, enabling
the folder permissions for all services.
This also fixes folder-related tests to set up appropriate user
permissions.
This should only be merged right after alphagov/notifications-api#2428,
when all other permission stories are done.
User model is the most natural place for a permission check method,
however this means that we need to pass the full user object to
service model methods and TemplateList instead of user_id.
Putting the permission check in the get_user_template_folders allows
us to replace `all_template_folders` usage with the new method without
having to worry about the temporary service permission flag.
