Add the new Navigation to core as an Experimental module

Problem/Motivation Add a new Administrative Navigation Toolbar in core being current worked in the Navigation contrib module after proposing [#3364258]. Proposed resolution Add the new Navigation Toolbar in core as beta. The Roadmap to Stable can be found at [#3421969]. We tested and validated a left, vertical toolbar because it performs better with large or complex menus like the one we use for Drupal’s administration interface.