Spec Text:
https://tc39.es/proposal-temporal/#sec-temporal.plaindate.prototype.toplainmonthday
https://tc39.es/proposal-temporal/#sec-temporal.plaindate.prototype.toplainyearmonth
https://tc39.es/proposal-temporal/#sec-temporal.plaindatetime.prototype.toplainyearmonth
https://tc39.es/proposal-temporal/#sec-temporal.plaindatetime.prototype.toplainmonthday


Bug: v8:11544
Change-Id: Ia97de3b4dde183ae4ee514deb4d13da5d5ff9bae
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3534451Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Frank Tang <ftang@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80680}