Spec text:
https://tc39.es/proposal-temporal/#sec-temporal.plaindatetime.prototype.withplaintime

Bug: v8:11544
Change-Id: I5277fb88675bb6d99b028a289329db06b95cc003
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3565026
Commit-Queue: Frank Tang <ftang@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80706}