Implement self-signed cert generation. am: ccf4a3c9fd am: cc8d8e3480

Original change: https://android-review.googlesource.com/c/platform/system/keymaster/+/1532217

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I50ea2c110abbfcf6a32a027387ac94b4e5f39b20