This adds testing configs to the V8 side, so that they can be deleted on the
infra side in a follow up.

TBR=yangguo@chromium.org
NOTRY=true

Bug: v8:7302
Change-Id: I93e65576b9799675ea0a8beca188c84a30695de3
Reviewed-on: https://chromium-review.googlesource.com/867037Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50597}