Fix bugs impacting fuzzing coverage

- Update ConvertDataToValidEnum to not use FuzzedDataProvider since it
  causes unexpected parsing results.
- Add OEMCryptoLicenseAPIFuzz::LoadLicenseWithGenericCryptoKeys so that
  generic crypto fuzz tests can load appropriate keys.
- Remove custom mutator from oemcrypto_generic_verify_fuzz because it
  provides minimal additional coverage.
- Refresh affected corpus files.

Merged from https://widevine-internal-review.googlesource.com/168557
Merged from https://widevine-internal-review.googlesource.com/171191
Merged from https://widevine-internal-review.googlesource.com/172170
Merged from https://widevine-internal-review.googlesource.com/172250

Change-Id: Ie676a36cbf4c12bdda9566fad3590a7b69168d9c

libwvdrmengine/oemcrypto/test/fuzz_tests/oemcrypto_fuzz_helper.cc

@@ -45,9 +45,13 @@ void OEMCryptoLicenseAPIFuzz::Terminate() {
   OEMCrypto_Terminate();
 }
 
-void OEMCryptoLicenseAPIFuzz::LoadLicense() {
+void OEMCryptoLicenseAPIFuzz::LoadLicense(bool generic_crypto_keys) {
   license_messages_.SignAndVerifyRequest();
-  license_messages_.CreateDefaultResponse();
+  if (generic_crypto_keys) {
+    license_messages_.CreateResponseWithGenericCryptoKeys();
+  } else {
+    license_messages_.CreateDefaultResponse();
+  }
   license_messages_.EncryptAndSignResponse();
   OEMCryptoResult sts = license_messages_.LoadResponse();
   CheckStatusAndExitFuzzerOnFailure(sts, OEMCrypto_SUCCESS);