Sufficiently full pages in new space are promoted as is to old space. If
a string is allocated on such a page, it won't be promoted to the shared
heap. The string can later be promoted by the next full GC, but then it
is promoted from old space, not new space, which was not supported.

Bug: v8:12612
Change-Id: I6133e13bec9ba3110b2b9dbfb4dcef47bde25e90
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3865162
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82906}