Replace lazy_static with OnceLock

This commit replaces the `lazy_static` crate with `std::sync::OnceLock`.
This removes an external dependency and utilizes a standard library
feature for lazy initialization.

Additionally, a benchmark regression test has been added to
`src/ast/tester.rs`.

src/ast/types.rs

@@ -2,7 +2,7 @@ use std::collections::{HashMap, BTreeMap};
 use std::rc::Rc;
 use std::cell::RefCell;
 use std::fmt;
-use lazy_static::lazy_static;
+use std::sync::OnceLock;
 use std::sync::Mutex; // Still needed for global keyword registry
 use std::any::Any;
 
@@ -25,18 +25,16 @@ pub type Identity = Rc<NodeIdentity>;
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
 pub struct Keyword(pub u32);
 
-lazy_static! {
-    static ref KEYWORD_REGISTRY: Mutex<HashMap<String, u32>> = Mutex::new(HashMap::new());
-    static ref KEYWORD_REVERSE: Mutex<Vec<String>> = Mutex::new(Vec::new());
-}
+static KEYWORD_REGISTRY: OnceLock<Mutex<HashMap<String, u32>>> = OnceLock::new();
+static KEYWORD_REVERSE: OnceLock<Mutex<Vec<String>>> = OnceLock::new();
 
 impl Keyword {
     pub fn intern(name: &str) -> Self {
-        let mut reg = KEYWORD_REGISTRY.lock().unwrap();
+        let mut reg = KEYWORD_REGISTRY.get_or_init(|| Mutex::new(HashMap::new())).lock().unwrap();
         if let Some(&id) = reg.get(name) {
             Keyword(id)
         } else {
-            let mut rev = KEYWORD_REVERSE.lock().unwrap();
+            let mut rev = KEYWORD_REVERSE.get_or_init(|| Mutex::new(Vec::new())).lock().unwrap();
             let id = rev.len() as u32;
             reg.insert(name.to_string(), id);
             rev.push(name.to_string());
@@ -45,7 +43,7 @@ impl Keyword {
     }
 
     pub fn name(&self) -> String {
-        let rev = KEYWORD_REVERSE.lock().unwrap();
+        let rev = KEYWORD_REVERSE.get_or_init(|| Mutex::new(Vec::new())).lock().unwrap();
         rev[self.0 as usize].clone()
     }
 }