[Suggestion] Add a blacklist/whitelist for structure generation

[PiekarekLukasz]

Not sure if id call it a bug but here we go
Currently structures seem to spawn in most modded dimensions, even ones based on floating islands.
(for example those from immersive portals)

Could we get a blacklist or a whitelist for that?
Alternatively i think it wouldn't be that bad to restrict the structures to overworld only.