Some scrollers in Realms screens do not use the scroller background texture

Closely relates to MC-269616 and MC-269749.

The bug

Most scrollers use the file scroller_background.png behind the field the scroller can be moved to (exceptions include MC-269616 and MC-269749). However, some screens in Minecraft Realms menus do not for some reason, which is unintended.

This seems to coincide with scrollers that do not properly render translucent pixels in the scroller texture - see MC-269619, MC-269755 and MC-269763.

How to fix

Render the scroller background behind the scrollable field (and make sure it supports translucency, too).

Further notes

This ticket is based off of observations from the image attached to MC-269763.