This lets embedder to produce an id with sufficient entropy to
facilitate an id appropriate for a multi-process system and
immune to regular RNG seed being overriden, while maintaining
deterministic id allocation for tests.

Design doc: https://docs.google.com/document/d/1vGVWvKP9FTTX6kimcUJR_PAfVgDeIzXXITFpl0SyghQ
Related blink-side change: https://chromium-review.googlesource.com/c/chromium/src/+/2600273

Bug: v8:11268
Change-Id: I1a4d12463cf56d4378859dfa3ee4d717e176d468
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2600442Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Andrey Kosyakov <caseq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71864}