spdm: Implement transcript hash + sign helpers

Add some helpers for transcript hash and signing functionalities. The
key exchange operation involves many functionalities so it is separated
into several CLs.

BUG=b:284404632
TEST=spdm unittests

Change-Id: I3f5e7e29d787ebca34f95a008cb211d05ff966ea
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/spdm/+/4623480
Reviewed-by: Vadim Sukhomlinov <sukhomlinov@chromium.org>
Commit-Queue: Howard Yang <hcyang@google.com>
Tested-by: Howard Yang <hcyang@google.com>
13 files changed