Print ALL_VARIANTS and VARIANT_ALIASES when passing a wrong
--variants argument to tools/run-tests.py.

Change-Id: I6d4278633dd11990d0ace1c93f544213fbfc156e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2139579
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Tamer Tas <tmrts@chromium.org>
Reviewed-by: Tamer Tas <tmrts@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67039}