bug#56393: Actually fix the long lines display bug

[Eli Zaretskii]

> From: Ihor Radchenko <yantar92@gmail.com>
> Cc: Gregory Heytings <gregory@heytings.org>,  gerd.moellmann@gmail.com,
>   larsi@gnus.org,  56393@debbugs.gnu.org
> Date: Sat, 09 Jul 2022 20:09:42 +0800
> 
> I am not sure if it is related, but I do observe a slowdown when moving
> across fontified buffer. This happens in really large buffers when
> moving across invisible text. AFAIU, line-move-1 uses
> next-single-property-change loop, which could be costly when the region
> has a large number of discontinuous text properties.

Invisible text is a different matter altogether.  The problem there is
that the amount of text on the screen is very different from what's
actually in the buffer, and moving through such a buffer needs to skip
the invisible text, which isn't free.

Face properties don't have such an effect.