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

@@ -868,7 +868,7 @@ pub fn fork_dim_merge(
             };
             if tid_dim > inner_idx {
                 let new_tid = Node::ThreadID {
-                    control: new_fork_id,
+                    control: new_fork,
                     dimension: tid_dim - 1,
                 };
                 let new_tid = edit.add_node(new_tid);
@@ -876,7 +876,7 @@ pub fn fork_dim_merge(
                 edit.sub_edit(tid, new_tid);
             } else if tid_dim == outer_idx {
                 let outer_tid = Node::ThreadID {
-                    control: new_fork_id,
+                    control: new_fork,
                     dimension: outer_idx,
                 };
                 let outer_tid = edit.add_node(outer_tid);
@@ -894,7 +894,7 @@ pub fn fork_dim_merge(
                 edit = edit.replace_all_uses(tid, rem)?;
             } else if tid_dim == inner_idx {
                 let outer_tid = Node::ThreadID {
-                    control: new_fork_id,
+                    control: new_fork,
                     dimension: outer_idx,
                 };
                 let outer_tid = edit.add_node(outer_tid);