feat: gc-arena

finally...

src/ty/internal/list.rs

@@ -1,12 +1,11 @@
 use hashbrown::HashSet;
 
 use derive_more::Constructor;
-use gc_arena::{Arena, Collect, Rootable};
+use gc_arena::Collect;
 use rpds::Vector;
 
-use crate::error::Result;
 use crate::ty::public as p;
-use crate::vm::{GcRoot, VM};
+use crate::vm::VM;
 
 use super::Value;