Adds a new property to the CDM's QueryStatus called QUERY_KEY_SYSTEM_ID that
contains the System ID. (as read from OEMCrypto_GetKeyData) Adds a new
property to the DrmPlugin (cleverly named "systemId") that allows the app to
query for this. Also adds unit tests.
Also changes the Device ID getter in crypto_engine.cpp to return a failure
instead of an empty ID.
Bug: 8621632
Merge of https://widevine-internal-review.googlesource.com/#/c/5010/ from
widevine cdm repository to android repository.
Change-Id: I8f309af18487c499e8ce25e829059e45623ea4dc