Merged from http://go/wvgerrit/69723.
The new APIs are getOfflineLicenseIds, getOfflineLicenseState and
removeOfflineLicense. These methods are currently stubbed out in
Widevine hidl service. This CL completes the implementation.
Test: unit tests - libwvdrmdrmplugin_hidl_test
Test: GTS
--test com.google.android.media.gts.MediaDrmTest#testWidevineApi29
bug: 117570686
Change-Id: I96ffb75f453e36e931effefd3664b5faa8d69d30