Restore notification sounds in 2 passes from backup

 Add a 2nd notification channel sound Uri restore attempt
  when package state has changed: add/update etc.
 Backup & Restore will restore NotificationManagerService before app
  packages are installed, resulting in notification channels losing
  custom sound configurations.

 Also: android.resource:// URIs should not be canonicalized => it always
  returns null.

Test: atest PreferencesHelperTest
Bug: 158351264

Change-Id: I9377afe811e601ad30a1059e7576828fa38e7aca