setUnicodeKeywordValue doesn't remove unrelated keyword/value pairs
when the locale is too long, which causes NumberFormat to fail when
calling createInstance. Fix this by using LocaleBuilder to add keyword/value
into a new locale instead of removing the keyword.

Also see https://unicode-org.atlassian.net/browse/ICU-20862

Bug: chromium:1012579
Change-Id: I0f664f60dad8fe786443c8ca8b21ea43323cbf49
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1855586Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Frank Tang <ftang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64253}