ID attestation: Define tag for a second IMEI

Define a KeyMint tag for a second IMEI to be included in the attestation
record.

Also clarify that the IMEI tag is meant to include one, and only one,
IMEI.

Bug: 244732345
Test: android.keystore.cts.DeviceOwnerKeyManagementTest
Merged-In: I70ecbb0245ba2e517e5d0db0cfdce4525846f3e5
Change-Id: I70ecbb0245ba2e517e5d0db0cfdce4525846f3e5
2 files changed