[Multi-user] Make various backup settings be per-user

Use the "forUser" variation of getting/putting settings for the
following backup settings:
- backup_auto_restore
- backup_transport
- packages_to_clear_data_before_full_restore

Bug: 121305979
Test: 1) atest RunBackupFrameworksServicesRoboTests
2) Verify default auto restore is true;
Toggle auto restore in UI -> changes UserBMS state;
Change current transport via bmgr -> changes UserBMS state;
Check settings for user 0 different from user 10;
3) Run backup pass, restore pass

Change-Id: I69e2a4f9c870dd7b5661dfa17f891384825926f5