Refactor UsageInfo and SubstitutionMap

This commit refactors the `UsageInfo` struct to use a single
`HashSet<Address>` for both used and assigned addresses, simplifying the
logic. It also updates the `SubstitutionMap` to use a similar approach
for tracking assigned values.

Key changes include:
- `UsageInfo` now has `used` and `assigned` fields of type
  `HashSet<Address>`.
- `SubstitutionMap`'s `add_local`, `add_global`, `add_upvalue`,
  `remove_local`, `remove_global`, and `remove_upvalue` methods have
  been replaced with a generic `add_value` and `remove_value` that
  operate on `Address`.
- The `Optimizer`'s `collect_pattern_usage` and `visit_node` methods
  have been updated to use the new `UsageInfo` and `SubstitutionMap`
  APIs.
- `Get` and `Set` nodes now use `sub.map_address` to transform addresses
  based on the current substitution.

src/ast/compiler/binder.rs

@@ -118,7 +118,10 @@ impl Binder {
         if self.functions.len() == 1 {
             let mut globals = self.globals.borrow_mut();
             if globals.contains_key(name) {
-                return Err(format!("Global variable '{}' is already defined.", name.name));
+                return Err(format!(
+                    "Global variable '{}' is already defined.",
+                    name.name
+                ));
             }
             let idx = globals.len() as u32;
             globals.insert(name.clone(), idx);
@@ -512,7 +515,10 @@ mod tests {
         if let BoundKind::Lambda { body, .. } = &bound.kind {
             if let BoundKind::Block { exprs } = &body.kind {
                 let x_decl = &exprs[0];
-                if let BoundKind::Define { captured_by, addr, .. } = &x_decl.kind {
+                if let BoundKind::Define {
+                    captured_by, addr, ..
+                } = &x_decl.kind
+                {
                     assert!(matches!(addr, Address::Local(_)));
                     assert!(
                         !captured_by.is_empty(),
@@ -544,7 +550,10 @@ mod tests {
         if let BoundKind::Lambda { body, .. } = &bound.kind {
             if let BoundKind::Block { exprs } = &body.kind {
                 let x_decl = &exprs[0];
-                if let BoundKind::Define { captured_by, addr, .. } = &x_decl.kind {
+                if let BoundKind::Define {
+                    captured_by, addr, ..
+                } = &x_decl.kind
+                {
                     assert!(matches!(addr, Address::Local(_)));
                     assert!(
                         captured_by.is_empty(),