bug#57150: 29.0.50; [PATCH] Add test coverage for overlay modification hooks

[Eli Zaretskii]

> Cc: 57150@debbugs.gnu.org
> From: Ihor Radchenko <yantar92@gmail.com>
> Date: Mon, 15 Aug 2022 12:14:37 +0800
> 
> At least, Org mode can greatly benefit from faster overlays.

The problems with overlays in Emacs are much wider than just Org.  Our
performance sucks in many cases because of that.  Just two examples
that were mentioned lately in the "long-line optimizations"
discussion: show-paren-mode and isearch-lazy-highlight -- each one of
these two is capable of literally bringing Emacs to its knees,
response-time wise.