Update unit tests for v15.2

Merge from Widevine repo of http://go/wvgerrit/77609

For v15.2 we require that nonces not collide across sessions and there are
restrictions placed on the mac key's IV in LoadKeys.

Test: ran unit tests on reference code

Bug: 131325434
Bug: 131326334

Change-Id: I1bb01c30d8c15d66d762c28b57d7700c44daa835

libwvdrmengine/oemcrypto/test/oec_session_util.h

@@ -81,6 +81,7 @@ typedef struct {
 struct MessageData {
   MessageKeyData keys[kMaxNumKeys];
   uint8_t mac_key_iv[KEY_IV_SIZE];
+  uint8_t padding[KEY_IV_SIZE];
   uint8_t mac_keys[2 * MAC_KEY_SIZE];
   uint8_t pst[kMaxPSTLength];
 };