Make old cave generation more claustrophobic

Old caves should have more width variation to them, possibly squeezing from 4-5 blocks wide all the way down to 1-3 block-wide tunnels. Caving IRL is a lot about squeezing into tight, unwelcoming, almost alien places where you don't necessarily know if there's a way out, and where you don't know what's ahead of you. You push ahead and crawl to hopefully land somewhere new and twisted.

Having old caves sometimes becoming narrow tunnels would also create interesting opportunities where, in some caves;

• You can't really sprint away from danger, if you encounter it;
• You follow a tight tunnel not knowing where it leads, hoping for an exit up ahead;
• You maybe don't have torches and claustrophobia kicks in;
• You burrow into the tunnel to follow the flow of the cave and venture deeper still