https://tc39.es/proposal-intl-segmenter/

TC39 passed Intl.Segmenter to stage 3 in Jul 21.
This CL move our earlier prototype to the current spec.

Bug: v8:6891
Change-Id: I07234beed54f671c26bdbfb3983c5bc2fa5a29b0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2219413Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Frank Tang <ftang@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Frank Tang <ftang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69080}