`Array::insert` violates exception safety if compare function panics, leading to potential Double-Free

Summary

In affected versions of this crate, `Array::insert` is not exception safe. In the `UPSERT` path, `key` and `value`'s snapshot is written to `self.data_block`, and after the insertion is completed, `key` and `value` are `mem::forget` in order to prevent double free. However, during the insertion, `K::compare` is invoked, which is a user-provided method. If user deliberately call panic in this function, during unwinding, the destructors of `key`, `value`, and `self` will all be called (since the `mem::forget` has not been called yet), leading to Double Free. Similar issues happens in the `!UPSERT` path.

The soundness issue was fixed in version `3.8.4` by using `ManuallyDrop` instead of `mem::forget`, and separating fallible code from infallible code during a node split - insert = insert_try -> insert_unchecked.