[ Merge of http://go/wvgerrit/174470 ]
There are two sets of changes
* Mocking CryptoSession so that OEMCrypto API version can be queried
* Creating a PolicyEngineTestV16 so that API version expectations
can be set and V18 can be accommodated.
Bug: 278751387
Test: policy_engine_unittest
Change-Id: Ied664ce87e22f697b6a45d3c573e22273e65e37f