macos: Provide Edit menu with actions for undo/copy/paste
Handle common commands (cut/copy/paste/delete/select-all/undo/redo) at application level.
This MR adds an Edit menu to the default menu bar. The actions from the Edit menu bar work for both GTK and native widgets. The action names follow the names used for text/label widgets.
Fixes #6829 (closed)
This is an alternative to !7797 (closed).
Edited by Arjan Molenaar