Support detecting generated ancient chunks

[BrainStone]

Alright, so it took me a bit of messing around to figure this one out.

In all honesty, I'm not sure how sensical this change is, but it does fix my issue. I'll be doing a tad more testing later to see if the data I'm seeing is the result of some weird stuff I did to the worlds or if it's actually vanilla data.
I decided to forgo the lighting check, for the reason that the only way the world pattern makes sense is just for loading all chunks anyways and I figured loading these chunks is safe, as just lighting is missing.

I won't be mad if you don't merge this either. This is primarily for fixing the issue I came across myself and I'm unsure of how applicable this is for general audiences.