- Rely on GCCallbacksScope to avoid nesting callbacks.
- Use a single entrypoint consistently for all callsites.

Change-Id: I6be1f749a2d6bfc9d5db4c84c753e9176472bce2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3605821Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80268}