bug#56682: Fix the long lines font locking related slowdowns

[Eli Zaretskii]

> Date: Thu, 04 Aug 2022 10:33:48 +0000
> From: Gregory Heytings <gregory@heytings.org>
> cc: gerd.moellmann@gmail.com, 56682@debbugs.gnu.org, 
> monnier@iro.umontreal.ca, 
>     dgutov@yandex.ru
> 
> navigating through the locales.json file was slow (at some positions) 
> before the change and is now reasonably fast (but alas not instantaneous).

Which navigation commands were slow, as compared to the same commands
in other portions of this file?