[Multi-user] Make backup and initialize receivers per user

Makes the PendingIntent and BroadcastReceiver for running backup and
initialize operations tied to a specific user. Also some style cleanup.

Bug: 121305979
Test: 1) atest RunBackupFrameworksServicesRoboTests
2) adb shell bmgr clear [transport] -> init successfully
3) adb shell bmgr run -> backup successful
4) adb shell bmgr enable false -> runs device init successfully
Change-Id: Ic3f411fbf97c758974a0af10a36e4812d19a534d