Update calls to UsageStatsService to include package names.

All events being reported need to include a package name.
Updating calls from AMS to use the pre-defined
Event.DEVICE_EVENT_PACKAGE_NAME instead of "android" or null.

Bug: 138323439
Test: builds and no error logs seen regarding null events being reported.
Change-Id: I65653e17a5c37cae5aff470433b86cd71e5f1d9a