feat: Implement closure cracking and inlining

Introduces a new optimizer pass that can "crack" closures, allowing for
more aggressive specialization. It also enables inlining of upvalues
that point to immutable global variables. This removes overhead for
higher-order functions and currying when arguments are statically
resolvable.

src/ast/compiler/mod.rs

@@ -6,6 +6,7 @@ pub mod dumper;
 pub mod macros;
 pub mod type_checker;
 pub mod specializer;
+pub mod optimizer;
 pub mod lambda_collector;
 
 pub use binder::*;
@@ -16,3 +17,4 @@ pub use dumper::*;
 pub use macros::*;
 pub use type_checker::*;
 pub use specializer::*;
+pub use optimizer::*;