Calling memset directly is faster than std::fill for multi-byte element
types.

Change-Id: I83b997740146688f87b86901825e31d6644bc25b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3687700
Auto-Submit: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80945}