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

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

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Iac28faafc3980ee813d904961d9fc8ac77d33755