This is represented as an extra, special value for the AllowChannels field in ZenPolicy, with special treatment.
Bug: 327419222
Bug: 331267485
Test: atest ZenModeTest
Flag: android.app.modes_ui
Change-Id: I44440e40e729d295150b36beda824ddbfa1f170d
modifying the corresponding methods on ZenModesBackend to collect that information from NotificationManager.
Bug: 327419222
Test: ZenModesBackendTest, ZenModeTest
Change-Id: I01cb0ffa21a7fecaa5128cec51ced3eff384f370