Make world border rendering interact better with render distance/fog

[muzikbike]

Request Description

Vanilla's current handling of the world border is questionable - much like clouds, it abruptly cuts off at the render distance limit, instead of softly transitioning out of view with fog like other things in the world.

When at a far distance from the border, while within it, it will fade out as to not be visible, and will fade in as you approach it. This effect scales with render distance, which can appear strange:

When at a far distance from the world border while outside it, the game makes no attempt to fade it out. It renders at full intensity regardless of how far away it is. (https://bugs.mojang.com/browse/MC-225823) The left and right edges are also very clearly defined.

In line with the changes to clouds it may be worth changing how the world border interacts with render distance in Sodium to have it fit in with other elements of the world in a way that makes visual sense.