Cave structures generating on the surface

[careeoki]

A fix doable right now is just to set the max_height of the biome lower. But every cave entrance being the same is boring. This only seems to affect certain structures, maybe? Stalagmites and ground_patches in these examples. I haven't seen misplaced boulders or stone forest trees.

[IntegratedQuantum]

Stalagmites (and crystals) are generated outside of the structure system, which explain why they behave differently. Ground patches are a different problem though, I suspect it's just continuing an underground ground patch on the surface here.