CryptoSession: handle 0-length buffer in DecryptSample

In `Combine Decrypt Calls to OEMCrypto`,
OEMCrypto_ERROR_BUFFER_TOO_LARGE is used as the default error code to
signal fallback to legacy decrypt (sending subsamples separately).
The error code would not be updated if no calls to OEMCrypto were
made (e.g. 0-length buffers).

This change resets error code to OEMCrypto_SUCCESS after fall back to
legacy decrypt. Consequently, buffers that do no require OEMCrypto
calls would return OEMCrypto_SUCCESS.

Merge of http://go/wvgerrit/96743

Bug: 150188155
Test: GtsMediaTestCases
Test: DashTest#testWidevineH264AdaptiveWithRendererDisabling
Change-Id: Ib23803c51f16bc809bda5c2720e628e81f1df1dc

libwvdrmengine/cdm/core/src/crypto_session.cpp

@@ -2692,6 +2692,7 @@ OEMCryptoResult CryptoSession::DecryptSample(
 
   if (sts == OEMCrypto_ERROR_BUFFER_TOO_LARGE) {
     // Fall back to sending each subsample region individually
+    sts = OEMCrypto_SUCCESS;
     OEMCrypto_SampleDescription fake_sample = sample;
     for (size_t i = 0; i < sample.subsamples_length; ++i) {
       const OEMCrypto_SubSampleDescription& original_subsample =