This is in anticipation for sharing internalized and
in-place-internalizable strings across Isolates. When such strings are
shared, background compilation threads need to be able to allocate
strings in the shared old space.

Bug: v8:12007
Change-Id: I93179c9674cc16e5a6125049d20e61495bc1f3a9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3283615Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77959}