appIconMenu: Sync windows section with app menu

Keep the app icon context menu consistent with the app menu, so stop
grouping windows by workspace and add a section heading.

#968
1 job for wip/fmuellner/app-menu-refinement in 2 minutes and 47 seconds (queued for 1 second)
Status Job ID Name Coverage
  Source Check
passed #214773
js_check

00:02:47