This is a reland of commit 8ba60b7a

Changes to original:
- Weaken DCHECK in MakeThin to allow direct transitions of shared
  strings during deserialization. This is safe as the string to be
  transitioned is freshly created and hasn't escaped the thread yet.
  - To enable this, add has_active_deserializer() to LocalIsolate

- Shared thin string transitions are subject to the same layout changes
  as non-shared thin string transitions, thus treat them equally when
  checking if a map transition is safe.

Original change's description:
> [string] Non-transitioning shared strings
>
> Instead of transitioning shared strings to ThinString on
> internalization, use a forwarding table to the internalized string and
> store the index into the forwarding table in the string's hash field.
>
> This way we don't need to handle concurrent string transitions that
> modify the underlying string data.
>
> During stop-the-world GC, live strings in the forwarding table are
> migrated to regular ThinStrings.
>
> Bug: v8:12007
> Change-Id: I6c6f3d41c6f644e0aaeafbf25ecec5ce0aa0d2d8
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3536647
> Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
> Reviewed-by: Jakob Linke <jgruber@chromium.org>
> Reviewed-by: Shu-yu Guo <syg@chromium.org>
> Reviewed-by: Igor Sheludko <ishell@chromium.org>
> Commit-Queue: Patrick Thier <pthier@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#79801}

Bug: v8:12007
Change-Id: I022e5c4768b763a86bb28c9c82218c3b807371a0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3571817Reviewed-by: Shu-yu Guo <syg@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Jakob Linke <jgruber@chromium.org>
Commit-Queue: Patrick Thier <pthier@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80183}