- Add a comment on the macro that registers a prefinalizer.
- Refactor the API to avoid exposing internal types needlessly.

Change-Id: Ia88e786304616848556263410a8f5398c5374533
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3497766Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79334}