- Get rid of an unnecessary call to uloc_canonicalize in js-locale.
- Do not use regex, but rely on ICU for the structrural validity check
with Chrome's ICU or ICU 63 or newer. Otherwise, continue to use regex.

This became possible thanks to a couple of bug fixes in ICU ToT that
were cherry-picked for Chromium's ICU.

Not yet done is to change js-locale to use CanonicalizeLocale().
That will make a few more tests pass.

Bug: v8:8135
Test: test262/intl402/Intl/getCanonicalLocales/*
Test: test262/intl402/Locale/*
Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I45c10b298fb041e0b39a4d96309c68a7966f91c2
Reviewed-on: https://chromium-review.googlesource.com/c/1215223
Commit-Queue: Jungshik Shin <jshin@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56399}