message: feat(vm) Remove cloning the export in `Instance::lookup`.
  This patch does 2 things:
  1. It simplifies the code by using `?` on an `Option`,
  2. It then removes the need to clone the `export`.
diff: @@ -284,11 +284,8 @@ impl Instance {
  /// Lookup an export with the given name.
  pub fn lookup(&self, field: &str) -> Option<Export> {
  - let export = if let Some(export) = self.module.exports.get(field) {
  - export.clone()
  - } else {
  - return None;
  - };
  + let export = self.module.exports.get(field)?;
  +
  Some(self.lookup_by_declaration(&export))
  }
  