Refactor common functionality in note and sticker navigation

* sly.el (sly-highlight-face): Don't need this face.
(sly-flash-region): Use `highlight' as the default flashing face.
(sly-last-visited-note-buttons): Removed.
(sly--note-buttons-at): Removed.
(sly--search-note): Removed.
(sly-next-note): Alias to `sly-button-forward'
(sly-previous-note): Alias to `sly-button-backward'
(sly-goto-first-note): use `sly-next-node'
(sly-show-notes): Consider more than one button. Fancy flash
notes.
(sly-in-buffer-note): Add `sly-button-echo' property.
(sly--add-in-buffer-note): Add `sly-button-search-id' property.
(sly--compilation-note-group-button): Notes property is now
`sly-notes-group'
(sly--add-in-buffer-note): Notes property is now `sly-note'
(sly-note-filter-function): New variable.
(sly-next-note):

* contrib/sly-stickers.el (sly-stickers-prefix-map): Deleted.
(sly-stickers-mode-map): Restore previous simpler keybindings.
(sly-stickers--sticker): Use `sly-button-echo' property.
(sly-stickers--echo-sticker): Accept more stickers but assert they
are not there.
(sly-stickers--sticker): Add `sly-button-search-id' property.
(sly-stickers-next-sticker, sly-stickers-prev-sticker): Use
`sly-button-search'

* lib/sly-buttons.el (sly-action, sly-part): New `sly-button-echo'
property.
(sly-button-echo-button, sly-button-echo-part): New functions.
(sly-button--next-search-id, sly-button-next-search-id)
(sly-button--searchable-buttons-at, sly-button-search)
(sly-button-filter-function, sly-button-forward)
(sly-button-backward): New functions.

* lib/sly-tests.el (sly-test--compile-defun): Call
`sly-previous-note' interactively.
* sly.el (sly-maybe-show-compilation-log): Hide log if successp.

Not the other way around!