Remove RegulateISODate after BalanceISODate and inline one call to AddISODate
https://github.com/tc39/proposal-temporal/pull/2291/files

Spec Text:
https://tc39.es/proposal-temporal/#sec-temporal-addisodate
https://tc39.es/proposal-temporal/#sec-get-temporal.zoneddatetime.prototype.hoursinday

Bug: v8:11544
Change-Id: I4d5faaa48a26d37015c82bc06b3414698db9945d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3893558
Commit-Queue: Frank Tang <ftang@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83172}