Add test target for CrOS variations smoke test

Add an experimental test target for the Chrome OS variations smoke test.

Bug: b:202325793
Change-Id: Ib8523fd5c1aa2c9501a13cabffae75fc9ddbfc2a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3291875


Reviewed-by: Ben Pastene <bpastene@chromium.org>
Reviewed-by: Stephen Martinis <martiniss@chromium.org>
Commit-Queue: Kyle Shimabukuro <kyleshima@chromium.org>
Cr-Commit-Position: refs/heads/main@{#956772}