Unit tests for forbidden RSA key usage

This CL adds unit tests to verify that the following
forbidden uses of an RSA private key do not work:

- ForbidPrepAndSign -- A cast cert key cannot sign a license
  request.
- ForbidUseAsDRMCert -- A cast cert cannot be used with the
  DRM cert's padding scheme and it cannot be used to derive
  keys from a session key.
- *ForbidRSASignatureForDRMKey* -- A DRM cert key cannot be
  used with GenerateRSASignature.
- *OEMCertForbidGenerateRSASignature* -- An OEM cert key
  cannot be used with GenerateRSASignature.

Bug: 251875110
Change-Id: Ic2b23e3fd279e878c190a8294078a8d092126a29

libwvdrmengine/oemcrypto/test/oemcrypto_security_test.cpp

@@ -812,6 +812,7 @@ TEST_F(OEMCryptoLoadsCertificateAlternates,
     sts = OEMCrypto_GenerateRSASignature(s.session_id(), message_buffer.data(),
                                          message_buffer.size(), nullptr,
                                          &signature_length, kSign_PKCS1_Block1);
+    if (sts == OEMCrypto_ERROR_NOT_IMPLEMENTED) return;
     ASSERT_EQ(OEMCrypto_ERROR_SHORT_BUFFER, sts);
     ASSERT_NE(static_cast<size_t>(0), signature_length);
     vector<uint8_t> signature(signature_length);