[bssl] Make hkdf return Zeroizing type am: ccc52e5267 am: d817c68450 am: bc1537d844

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

Change-Id: I4874c8d625c1fb0dc97898cf8abd0df8a1731f04
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>