use proper byte sizes for ValueStack setup

This roughly shrinks initial allocation size under default config by 8.

Author: Robbepop

crates/wasmi/src/engine/executor/handler/state.rs

@@ -380,6 +380,11 @@ pub struct ValueStack {
 
 impl ValueStack {
     fn new(min_height: usize, max_height: usize) -> Self {
+        // We need to convert from `size_of<Cell>`` to `size_of<u8>`:
+        debug_assert!(min_height <= max_height);
+        let sizeof_cell = mem::size_of::<UntypedVal>();
+        let min_height = min_height / sizeof_cell;
+        let max_height = max_height / sizeof_cell;
         let cells = Vec::with_capacity(min_height);
         Self { cells, max_height }
     }