This replaces WeakFactory with FinalizationGroup.

New API is here: https://weakrefs.netlify.com/

BUG=v8:8179

Change-Id: I8c1c4a70deb42581d17117423dd29d93bdd35cb0
Reviewed-on: https://chromium-review.googlesource.com/c/1435938Reviewed-by: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59204}