Rework of the Y-axis

I think the Y-axis should be revamped with 1.17.  We should have a positive and negative Y-axis at something like Y=-512 to Y=512 so that mountains can generate high up and caves can have big caverns.  The sea level can be at Y=0 or something around it.  Also, there should be a gamerule about the F3 Menu whether you want the Y-level to be shown like this or a non-negative Y-value coordinate system like from Y=1 to Y=1024.  The chunk generation might be a bit buggy, I propose that we make smaller chunks like the Cubic Chunks Mod.