Fork fission bufferize

• Refactor fork fission, add fork fission bufferized version.
• Add test that uses fork fission to create extra forks.

hercules_opt/src/fork_transforms.rs

@@ -166,16 +166,6 @@ pub fn copy_subgraph(
     (new_nodes, map, outside_users)
 }
 
-fn is_strict_superset<T: Eq + Hash>(set1: &HashSet<T>, set2: &HashSet<T>) -> bool {
-    // A strict superset must be larger than its subset
-    if set1.len() <= set2.len() {
-        return false;
-    }
-
-    // Every element in set2 must be in set1
-    set2.iter().all(|item| set1.contains(item))
-}
-
 pub fn find_bufferize_edges(
     editor: &mut FunctionEditor,
     fork: NodeID,