[Multi-user] Support permission backup for multi-user

Bug: 123349308
Test: 1) atest RunBackupFrameworksServicesRoboTests
         2) atest CtsBackupTestCases
         3) atest CtsBackupHostTestCases
         4) atest GtsBackupTestCases
         5) atest GtsBackupHostTestCases

Manual testing (for system/secondary users):
  * Install Textra Sms (third-party sms client, requires sms
  permissions) and give permissions
  * adb shell bmgr --user [user-id] backupnow android
  * Uninstall and reinstall the app
  * abd shell bmgr --user [user-id] restore [token] android
  * Launch the app and verify permission dialog doesn't appear

Change-Id: I61ec4eb9c593465363dcf43059584b15f4aa81f5