[autotest] Support for new autotest artifacts.

This change updates dynamic_suites and provisioning to support the new
autotest build artifacts: control_files.tar and autotest_packages.tar.

In case these artifacts do not exist, it will then attempt to stage the
old autotest.tar artifact, thus still supporting older builds.

BUG=chromium:421122
TEST=Custom moblab build that successfully ran smoke suite against
2 images: 1 with autotest.tar and the other with the new artifacts.
CQ-DEPEND=CL:226822

Change-Id: If66026b46f77aaccaa83996e20a6749bad2b1625
Reviewed-on: https://chromium-review.googlesource.com/226823
Reviewed-by: Simran Basi <sbasi@chromium.org>
Commit-Queue: Simran Basi <sbasi@chromium.org>
Tested-by: Simran Basi <sbasi@chromium.org>
6 files changed