message: [pdsl_core] Add an important assertion to the storage::HashMap insert test
diff: @@ -26,6 +26,8 @@ fn insert() {
  assert_eq!(map.insert("1".into(), ", World!".into()), Some("Hello".into()));
  // Should *not* increase len.
  assert_eq!(map.len(), 1);
  + // Should return the new value
  + assert_eq!(map.get("1"), Some(&", World!".into()));
  }
  #[test]
  