This is a reland of ad5b005e

Original change's description:
> [snapshot] Expose the serializer through %SerializeDeserializeNow
>
> ... in order to exercise the snapshot/ component from mjsunit tests
> and fuzzers.
>
> * Since the serializer and deserializer can now be called at any time
> instead of only in a tightly controlled environment, several
> assumptions (such as an empty execution stack, no microtasks, no
> handles) no longer hold and had to be made configurable through
> SerializerFlags.
>
> * Root iteration now skips more root categories which were previously
> guaranteed to be empty (e.g. the stack, microtask queue, handles).
>
> * The %SerializeDeserializeNow runtime function triggers
> serialization, deserialization, and heap verification on the current
> isolate and native context.
>
> Support is not yet complete and will be extended in future work. Once
> all mjsunit tests successfully run, we can add a new test mode to
> stress serialization.
>
> Bug: v8:10416
> Change-Id: Ie7ff441a761257dd7f256d0a33e73227850074ac
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2159495
> Commit-Queue: Jakob Gruber <jgruber@chromium.org>
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Reviewed-by: Dan Elphick <delphick@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#67423}

Tbr: delphick@chromium.org,ulan@chromium.org
Bug: v8:10416
Change-Id: Ibed04c0f0b72fabcf811d8b18a1479391a11568b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2170090Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Dan Elphick <delphick@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67426}