[bssl] Make hkdf return Zeroizing type am: ccc52e5267 am: d817c68450

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Virtualization/+/2769600

Change-Id: If29fcae8634103deb36b40bad06e7cb39c20aa31
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>