spdm: Add tests package for integration test

This CL only adds the basic structure of the test directory, leaving
most trait implementations empty.

BUG=b:338528575
TEST=spdm unittests

Change-Id: I9c6dbc624a2e5121a8b736d7e069e5e9e356f300
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/spdm/+/5514870
Commit-Queue: ChromeOS Auto Retry <chromeos-auto-retry@chromeos-bot.iam.gserviceaccount.com>
Tested-by: Howard Yang <hcyang@google.com>
Reviewed-by: Vadim Sukhomlinov <sukhomlinov@google.com>
6 files changed