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`.

Cargo.toml

@@ -6,7 +6,6 @@ default-run = "myc"
 
 [dependencies]
 eframe = "0.33.3"
-lazy_static = "1.4.0"
 clap = { version = "4.5", features = ["derive"] }
 chrono = "0.4"
 regex = "1.10"