Refactor the interface between intl and Temporal and pass
the nanosecond in BigInt to intl. Approximate the nanoseconds
to the correct close by millisecond depending on the usage
before calling ICU API and convert the result millisecond into
BigInt in nanosecond before return from intl.

Remove Maybe for function always complete.

Bug: v8:11544
Change-Id: Icc471b80312c513c9415b690804aa624df4a387d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3897165Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Frank Tang <ftang@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83310}