Builtins are not snapshotted, but instead we insert "builtin wrappers"
into the snapshot, and create references to the corresponding builtin
when deserializing.

Subclassing builtins will be implemented in a follow-up CL.

First version: https://chromium-review.googlesource.com/c/v8/v8/+/3630080
Fix: initialize builtin_objects_handle_

Bug: v8:11525,v8:12820
Change-Id: Ia2b5d41af5d7f577f1b02356b22a8760963009e4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3635718Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80430}