This is a reland of 5320fe8d

Changes since revert:
- Remove stale DCHECK in deserializer

Original change's description:
> Reland "[string] Support shared strings in Value{Serializer,Deserializer}"
>
> This is a reland of 3cb4039c
>
> Changes since revert:
> - Fix FLAG_stress_scavenge interaction with shared Isolate
> - Use the shared Isolate's global handles to keep shared values
>   alive in transit during a postMessage
>
> Original change's description:
> > [string] Support shared strings in Value{Serializer,Deserializer}
> >
> > When FLAG_shared_string_table is true, postMessaging strings will share
> > instead of copy.
> >
> > Note that not all operations on shared strings are supported, and shared
> > strings may be slower than non-shared strings for some operations.

Bug: v8:12007
Change-Id: I70782978ed05558615eca03bafc4c12eba3644ca
Cq-Include-Trybots: luci.v8.try:v8_linux64_tsan_rel_ng
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3417189Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78791}