KeyMint VTS: local RSA encryption

Change RSA encryption (with public key) so it happens locally in the
test, rather than by invoking an ENCRYPT operation against KeyMint.

 - Specify MGF1 digest for OAEP mode as (now) required by AIDL spec.
 - Drop tests for too-long encryption inputs.
 - Adjust test comments to reflect decryption-only nature.
 - Change parameter checking tests to do so on DECRYPT rather than ENCRYPT.

Test: VtsAidlKeyMintTargetTest
Change-Id: I10c4beea28387eecfd0bc7c5dfd59a1b66fec21e
diff --git a/security/keymint/aidl/vts/functional/KeyMintAidlTestBase.h b/security/keymint/aidl/vts/functional/KeyMintAidlTestBase.h
index 1a14d47..d8f1bb3 100644
--- a/security/keymint/aidl/vts/functional/KeyMintAidlTestBase.h
+++ b/security/keymint/aidl/vts/functional/KeyMintAidlTestBase.h
@@ -165,6 +165,7 @@
     void LocalVerifyMessage(const string& message, const string& signature,
                             const AuthorizationSet& params);
 
+    string LocalRsaEncryptMessage(const string& message, const AuthorizationSet& params);
     string EncryptMessage(const vector<uint8_t>& key_blob, const string& message,
                           const AuthorizationSet& in_params, AuthorizationSet* out_params);
     string EncryptMessage(const string& message, const AuthorizationSet& params,