[rkp] Encrypt/decrypt the private key with AES-256-GCM am: 8b8e6e642e am: 13998f5bc3 am: 37cede3931 am: cc4e550d52

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

Change-Id: I1f1311dd98e19e536e415fad52ef4d82a4a070c1
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>