Add KeyPurpose::ATTEST_KEY. am: 7c13039711 am: 99ac9848df am: cad4604a2e

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/1534063

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I5340ad2ac563ef786eb5ad0a77f29d4dc13156fc