[ Merge of http://go/wvgerrit/100905 and http://go/ag/10708438 ] Add support for ATSC certificate and licenses handling. ATSC files are distinguished from the apps DRM certificate and licenses by file naming conventions. Bug: 139730600 Test: WV unit/integration test, GtsMediaTestCases Change-Id: I295f66f92fe01d7716978deac9dc360d74addedd