Previously, Intl.PluralRules was mostly implemented in JavaScript. This
patch moves most of the constructor and parts of other methods to C++.

The size of the Intl.PluralRules object is reduced by not storing
MinimumIntegerDigits, MinimumFractionDigits, MaximumFractionDigits,
MinimumSignificantDigits, MaximumSignificantDigits. Instead these are
looked up from icu::DecimalFormat as required.

Another optimziation is that we don't create the result of
resolvedOptions when the Intl.PluralRules object is constructed, but
instead defer until this method is called. In the future, we may want
to cache the result.

This patch also cleans up several error handling paths that shouldn't
happen with ICU and instead just crashes should it ever happen.

Bug: v8:5751
Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: I84c5aa6c25c35fe2d336693dee1b36bf3dcd4a79
Reviewed-on: https://chromium-review.googlesource.com/1158701
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Jungshik Shin <jshin@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54917}