... by replacing manual memory management with unique_ptrs.

Bug: v8:10416
Change-Id: Id3acb38192a5203bcb8c0f7eee774eacb934ef49
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2159492
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67334}