Hover text background box cannot be retextured

The bug

The box displayed behind text that shows up when hovering over items, things in Statistics, certain buttons and other situations cannot be retextured.

This may be considered a feature request, but it seems strange that something with somewhat intricate detailing around the edges would be code-generated rather than texture-based, as opposed to a box of solid color like was used in 2010-2011, especially given 23w31a's changes to UI texture handling (custom nine-slices, etc.)

How to fix

Introduce a texture file and accompanying mcmeta file for this box.