The icu object cache consists of 5 keys at most -> change it from
an unordered_set to a plain array.

Possible return values of CompareStrings are {-1,0,1}. Return those
directly instead of going through Factory::NewNumberFromInt.

Bug: v8:12196
Change-Id: Ia42bb6b1a0ebdc99550f604aa79cb438b150ee88
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3149454
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76746}