Refactor: Move utils to separate module

Moves `PathTracker` and `UsageInfo` to the `utils` module to improve
code organization.

src/ast/compiler/optimizer/inliner.rs

@@ -5,8 +5,8 @@ use std::cell::RefCell;
 use std::collections::{HashMap, HashSet};
 use std::rc::Rc;
 
-use super::substitution_map::{SubstitutionMap, UsageInfo};
-use super::utils::flatten_tuple;
+use super::substitution_map::SubstitutionMap;
+use super::utils::{flatten_tuple, UsageInfo};
 
 pub struct Inliner<'a> {
     pub globals: &'a Option<Rc<RefCell<Vec<Value>>>>,