Fix poor worst case performance of set intersection (and union, somewhat) on asymmetrically sized sets and extend unit tests slightly beyond that
Fix poor worst case performance of set intersection (and union, somewhat) on asymmetrically sized sets and extend unit tests slightly beyond that

graydon/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust