Improve sly-stickers

The single `sly-stickers-dwim' keybinding needs more work.

* sly-stickers.el (sly-stickers--flash-sticker): Flash stickers.
(sly-stickers--sticker): Behave correctly when setting stickers
from region.
(sly-stickers--set-sticker-piority): New helper.
(sly-stickers--increase-prio, sly-stickers--decrease-prio): Use it.
(sly-stickers-dwim): Deactivate mark after setting from region.
(sly-stickers-operate-on-sticker): "No stickers at point" is an
error.
(sly-stickers-commit-stickers): Use a second set of overlays.
(sly-stickers-fetch): Flash all stickers, but populate only the
ones with values.

* sly.el (sly-with-popup-buffer): New :hidden option for existing
`select' parameter.
(sly-with-popup-buffer): Add edebug spec.
(sly-flash-region): Make into cl-defun, and can flash multiple times.
(sly--highlight-line): Adjust call to sly-flash-region.
Stabilize `sly-stickers-dwim' behaviour

Also fix a ton of bugs

* sly-stickers.el (sly-stickers--stickers-exactly-at): New function.
(sly-stickers--sticker-map): Get rid of
`sly-stickers-operate-on-sticker'
(sly-stickers--sticker): Error when trying to make a sticker for same coordinates
(sly-stickers--sticker-substickers): Check invariants.
(sly-stickers-clear-region-stickers): New interactive function.
(sly-stickers-clear-buffer-stickers): Use -region variant.
(sly-stickers-clear-defun-stickers): Use -region variant.
(sly-stickers-dwim): Improve and document.
(sly-stickers-operate-on-sticker): Remove.
(sly-stickers--delete): Remove from hashtable too.
(sly-stickers-commit-stickers): Temporary stickers buffer is hidden.
(sly-stickers--set-tooltip): New function.
(sly-stickers--sticker, sly-stickers--arm-sticker)
(sly-stickers--disarm-sticker, sly-stickers--populate-sticker):
Use it.

* slynk-stickers.lisp (check-stickers): Correctly iterate value
lists.
Implement `sly-button-inspect' for stickers and fix bugs.

* sly-stickers.el (sly-stickers--sticker): Implement `sly-button-inspect' action

* slynk-stickers.lisp (find-sticker-or-lose): New function.
(inspect-sticker-values): New function.
(compile-for-stickers): Dead stickers are dead.