Revisit fast leaves culling other blocks

[muzikbike]

Request Description

I reported #2456 just under a year ago, which was fixed under d2a6815. This fix was ultimately reverted (e09bbe3), but I still wonder if there's a good way to implement this that doesn't cause other issues, since we can still get rid of a considerable amount of forest geometry this way. Combined with #2970, this could improve framerates considerably.