KeyMint: improve HAL spec and tests

- clarify & test BIGNUM spec
- allow alternative return codes when requesting device unique
  attestation
- use specific error for early boot import failure
- test more early boot key scenarios (in post-early-boot mode)

Test: VtsAidlKeyMintTargetTest
Change-Id: I70a342084a29144aef1ed0ff80fec02cc06ffbc0
diff --git a/security/keymint/aidl/vts/functional/DeviceUniqueAttestationTest.cpp b/security/keymint/aidl/vts/functional/DeviceUniqueAttestationTest.cpp
index 6f0ee4e..b0f056a 100644
--- a/security/keymint/aidl/vts/functional/DeviceUniqueAttestationTest.cpp
+++ b/security/keymint/aidl/vts/functional/DeviceUniqueAttestationTest.cpp
@@ -75,7 +75,7 @@
                                       .Authorization(TAG_DEVICE_UNIQUE_ATTESTATION),
                               &key_blob, &key_characteristics);
 
-    ASSERT_EQ(result, ErrorCode::INVALID_ARGUMENT);
+    ASSERT_TRUE(result == ErrorCode::INVALID_ARGUMENT || result == ErrorCode::UNSUPPORTED_TAG);
 }
 
 /*
@@ -101,7 +101,7 @@
                                       .Authorization(TAG_DEVICE_UNIQUE_ATTESTATION),
                               &key_blob, &key_characteristics);
 
-    ASSERT_EQ(result, ErrorCode::INVALID_ARGUMENT);
+    ASSERT_TRUE(result == ErrorCode::INVALID_ARGUMENT || result == ErrorCode::UNSUPPORTED_TAG);
 }
 
 /*