* lisp/outline.el: Don't set outline-minor font-lock text property 'keymap'.

* lisp/outline.el: Don't set outline-minor font-lock text property 'keymap'.

Instead of adding font-lock text property 'keymap' with
outline-minor-mode-cycle on headings in outline-minor-mode,
check for outline-minor-mode-cycle and outline-on-heading-p
in :filter on keys from the keymap of outline-minor-mode.
https://lists.gnu.org/archive/html/emacs-devel/2022-01/msg00180.html

(outline-minor-mode-cycle--bind): Add a condition on outline-minor-mode-cycle
and outline-on-heading-p in :filter.
(outline-font-lock-keywords): Remove if-branches for outline-minor-mode-cycle
that added keymap.
(outline-minor-mode-highlight-buffer): Don't put keymap on overlays.
(outline-minor-mode): Rewrite :keymap setting to rely on
easy-mmode-define-keymap, and add :inherit outline-minor-mode-cycle-map.
Don't check for outline-minor-mode-cycle to add font-lock keywords.
(outline--insert-open-button, outline--insert-close-button):
Remove :parent outline-minor-mode-cycle-map.