ctest: Move the remaining ctest capabilities to cros_au_test_harness

Ctest don't have much and it is calling cros_au_test_harness
anyway. After this we can call cros_au_test_harness directly.

Also deprecate finding target_image automatically. This logic is not
needed here and is fragile.

BUG=chromium:872441
TEST=relevant unittests
TEST=betty-release-tryjob

Change-Id: I32e816c1f8ad4a0f33231eef584499fa03713353
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crostestutils/+/1828293
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Commit-Queue: Amin Hassani <ahassani@chromium.org>
4 files changed