Move the 'GetTopLayerNode'-function to the data storage
Summary: Refactoring: Remove leading namespaces
Test Plan: manual testing
Reviewers: kislinsk, O1 MITK Core, floca
Reviewed By: kislinsk, O1 MITK Core, floca
Subscribers: floca, kalali
Maniphest Tasks: T24173
Differential Revision: https://phabricator.mitk.org/D148