Refactor VM to use trait objects for closures

The `CallFrame` struct and various VM methods now use `Rc<dyn Object>`
to hold closures, allowing for more flexibility and avoiding unnecessary
cloning.

This change also addresses the performance concern regarding deep copies
of closures, preferring `Rc<dyn Trait>` with local `downcast_ref` where
appropriate.

Additionally, a documentation note has been added to `gemini.md`
regarding this performance preference in Rust.

src/ast/environment.rs

@@ -261,12 +261,13 @@ impl Environment {
                 vec![],
                 *positional_count,
             ));
+            let closure_obj: Rc<dyn crate::ast::types::Object> = closure;
 
             return Rc::new(crate::ast::types::NativeFunction {
                 purity: Purity::Impure,
                 func: Rc::new(move |args| {
                     let mut vm = VM::new(global_values.clone());
-                    let res = match vm.run_with_args(&closure, args) {
+                    let res = match vm.run_with_args(closure_obj.clone(), args) {
                         Ok(v) => v,
                         Err(e) => panic!("Myc Runtime Error: {}", e),
                     };
@@ -287,9 +288,9 @@ impl Environment {
 
                 let mut final_res = res;
                 if let Value::Object(obj) = &final_res
-                    && let Some(closure) = obj.as_any().downcast_ref::<crate::ast::vm::Closure>()
+                    && obj.as_any().downcast_ref::<crate::ast::vm::Closure>().is_some()
                 {
-                    final_res = match vm.run_with_args(closure, args) {
+                    final_res = match vm.run_with_args(obj.clone(), args) {
                         Ok(v) => v,
                         Err(e) => panic!("Myc Runtime Error (Closure): {}", e),
                     };
@@ -396,8 +397,8 @@ impl Environment {
 
         while let Ok(Value::TailCallRequest(payload)) = result {
             let (next_obj, next_args) = *payload;
-            if let Some(closure) = next_obj.as_any().downcast_ref::<crate::ast::vm::Closure>() {
-                result = vm.run_with_args_observed(&mut observer, closure, next_args);
+            if next_obj.as_any().downcast_ref::<crate::ast::vm::Closure>().is_some() {
+                result = vm.run_with_args_observed(&mut observer, next_obj, next_args);
             } else {
                 result = Err(format!(
                     "Tail call target is not a closure: {}",