ICU 71 added new enum value UNUM_APPROXIMATELY_SIGN_FIELD
need to map to "approximatelySign"

We also discover a spec bug in
https://github.com/tc39/proposal-intl-numberformat-v3/issues/99

All the parts of formatRangeToParts should have a source "shared" for
the case that start and end are the same or very close.

Bug: chromium:1336865
Change-Id: I89142479989d3d2017d8cb89194db737710c38ed
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3717278Reviewed-by: Shu-yu Guo <syg@chromium.org>
Commit-Queue: Frank Tang <ftang@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81286}