feat: lots of optimization

* allocate vm stack on the stack
* use Rc instead of Arc
* optimize recursive attribute set

src/vm/test.rs

@@ -3,7 +3,7 @@ extern crate test;
 use test::{Bencher, black_box};
 
 use ecow::EcoString;
-use rpds::{ht_map_sync, vector_sync};
+use rpds::{ht_map, vector_sync};
 
 use crate::compile::compile;
 use crate::ir::downgrade;
@@ -64,7 +64,7 @@ macro_rules! list {
 
 macro_rules! attrs {
     ($($x:tt)*) => (
-        Value::AttrSet(AttrSet::new(ht_map_sync!{$($x)*}))
+        Value::AttrSet(AttrSet::new(ht_map!{$($x)*}))
     )
 }