Longer length of caves and less dead ends in 21w06a

Cave generation in 21w06a needs to be changed. There is a very low chance for giant caves and most don't last long before a dead end comes along. Also most amethyst deposits and not close to anything at all they should have some sort of entrance connect to them. I think that there should be a higher chance for "water caves" to actually lead into a big cave rather than a dead end at the bottom.