Update OEMCrypto calls to use substrings

Merge from master branch of Widevine repo of http://go/wvgerrit/66073
Merge from oemcrypto-v15 branch of Widevine repo of http://go/wvgerrit/64083

As part of the update to v15, LoadKeys, RefreshKeys, and
LoadEntitledContentKeys should all use offsets and lengths into the
message rather than a pointer for its parameters. The CDM, tests,
adapters, and OEMCrypto implementations are changed to reflect this.

Test: tested as part of http://go/ag/5501993
Bug: 115874964

Change-Id: I981fa322dec7c565066fd163ca5775dbff71fccf

libwvdrmengine/cdm/util/include/string_conversions.h

@@ -26,6 +26,7 @@ std::string HexEncode(const uint8_t* bytes, unsigned size);
 std::string IntToString(int value);
 int64_t htonll64(int64_t x);
 inline int64_t ntohll64(int64_t x) { return htonll64(x); }
+std::string BytesToString(const uint8_t* bytes, unsigned size);
 
 }  // namespace wvcdm