- Eliminates non-const reference parameters in test/unittests.

Bug: v8:9429
Change-Id: Ia7b41482811183324a62859d27fc263e4032219a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1794802Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63643}