Fix JSSegmentIterator::Create getting the unicode string as a raw object
pointer and then performing memory allocation which then invalidates it.
This changes SetTextToBreakIterator to return a handle instead.

Bug: v8:6891
Change-Id: I57e175b31e78a074a0b3c5a8fc26b4af05b4a752
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1667409
Commit-Queue: Dan Elphick <delphick@chromium.org>
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Auto-Submit: Dan Elphick <delphick@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62287}