Merge from Widevine repo of http://go/wvgerrit/96783
This CL updates the reference code, unit tests, and adapter to use the
new v16 function OEMCrypto_LoadDRMPrivateKey. This is just an API
change to allow ECC support in the future. The reference code does not
yet support ECC certificates, and the CDM code assumes that all
certificates have an RSA key.
Bug: 152558018
Test: unit tests on taimen and w/v16 mod mock.
Change-Id: I0793b416513b81b3d74849f0b58dbdc91f075ac6
56b836bda3