The test name alone isn't informative alone.

This CL prints the variant name during the progress reporting.

tested by running test262 with all variants

R=machenbach@chromium.org
CC=yangguo@chromium.org,sergiyb@chromium.org

Bug: v8:8728
Change-Id: I3d7d1fc6eacef3712d87404c7276fd5523bb445a
Reviewed-on: https://chromium-review.googlesource.com/c/1458156
Commit-Queue: Tamer Tas <tmrts@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59437}