[rkp] Encrypt/decrypt the private key with AES-256-GCM am: 8b8e6e642e am: 13998f5bc3 am: 37cede3931

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Virtualization/+/2770558

Change-Id: I8134abff785f4e049c09ce43e9b4eea464e12eae
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>