`current_application_settings` belongs on `Gitlab::CurrentSettings`
The initializers including this were doing so at the top level, so every object loaded after them had a `current_application_settings` method. However, if someone had rack-attack enabled (which was loaded before these initializers), it would try to load the API, and fail, because `Gitlab::CurrentSettings` didn't have that method. To fix this: 1. Don't include `Gitlab::CurrentSettings` at the top level. We do not need `Object.new.current_application_settings` to work. 2. Make `Gitlab::CurrentSettings` explicitly `extend self`, as we already use it like that in several places. 3. Change the initializers to use that new form.