Follow-up to 3187606d34
When the `enable_names` setting is false and the `full_name_requirement` setting is set to `required_at_signup`, the name field in the signup form should effectively be not required (and hidden). However, that is not actually the case at the moment because the `name-validation.js` mixin only checks for the `full_name_requirement` setting when determining whether the name field should block a new signup.
This commit fixes the issue by making the `full_name_required_for_signup` and `full_name_visible_in_signup` site attributes check for the `enable_names` setting themselves. This spares any consumers of these properties from having to remember to include a check for the `enable_names` setting.
e2129dc07c