Is your feature request related to a problem? Please describe.
This is a feature which exists in the current WordPress menus. If we want this block to be the cornerstone of a new and better menus page in WordPress admin (#16635) then we need to have this feature supported b/c the new menus need to behave identically.

Describe the solution you'd like
The Navigation block should support this toggle and both render and add newly published pages to its list of pages.

Note
While on the server at render time one could think of doing a diff between a list of published pages and the list in the currently rendering bloc, in the editor that would be weird as a newly added page would automatically make the post unsaved, since detecting a new page changes the contents of the Navigation block. Therefore this needs an UX discussion.