Also implement AO: CompareEpochNanoseconds
Spec Text:
https://tc39.es/proposal-temporal/#sec-temporal.instant.compare
https://tc39.es/proposal-temporal/#sec-temporal.instant.prototype.equals

Bug: v8:11544
Change-Id: I953a890250ff0bf29cd24e4638bf17ceb5f9bb2f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3382057
Commit-Queue: Frank Tang <ftang@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80959}