(1.20-pre1 - 24w07a) Menu background

[muzikbike]

As of 24w09a, the background used for menus is now used as-is. Previously, a copy of the dirt texture was used, which was darkened by the game, but it now uses a pre-darkened texture and the game does not apply any changes to it.

Implementing this into MC-TextureGen would be useful as it could be used to convert existing textures from resource packs into the new format.

[muzikbike]