bug#16514: 24.3.50; Region overlay looks bad on refined hunks in diff-mode

[Eli Zaretskii]

> From: Kévin Le Gouguec <kevin.legouguec@gmail.com>
> Date: Sun, 06 Dec 2020 16:39:04 +0100
> Cc: 16514@debbugs.gnu.org, Dmitry Gutov <dgutov@yandex.ru>
> 
> As long as point does not go past the refinement (before the comma), the
> region's background has the region face's background.
> 
> Once point moves past the refinement, only non-refined parts keep the
> region face's background; refined parts keep the refinement background.

This is expected, since we sort overlays so that the one whose extent
is larger wins.

To do anything else the overlays should have priorities.