* lisp/outline.el: Bind margin mouse event to cycle outlines (bug#57813)

* lisp/outline.el: Bind margin mouse event to cycle outlines (bug#57813)

(outline-minor-mode): In mode keymap bind
'right/left-margin mouse-1' to outline-cycle, and
'right/left-margin S-mouse-1' to outline-cycle-buffer.
(outline-hide-subtree, outline-show-subtree): Add save-excursion
to keep point unmoved after mouse click.
(outline-cycle): Add optional arg 'event' like in
outline-hide-subtree and outline-show-subtree, and
add save-excursion to keep point unmoved after mouse click.
(outline--make-button-overlay, outline--make-margin-overlay):
Put overlay property 'evaporate' to t.
(outline--insert-open-button, outline--insert-close-button):
Remove temporary attempts to bind margin-local mouse events.