This PR addresses feedback given in #90822

@isidorn @jeanp413 not a big fan of how this ends up adding a new field to the layout.ts class which is only used by zen mode. Why can this not be added to the transitionDisposables set that is called each time zen mode changes? There should be a disposable for each editor that gets the line number updated, no?

@isidorn Not sure if I'm not understanding something but transitionDisposables just have an add and clear methods, and we need a way to keep track if an editor have already been added to avoid adding it multiple times so I just moved editorWidgetSet inside this.state.zenMode object and used the onDidDispose event to remove the disposed editors from the set.

Let me know if I'm missing something