fixup! Implement backup/restore for network policy

Test:
1. Block an app's (e.g. Chromium) wifi and mobile data through the firewall
2. Backup to internal storage on user 0
3. Create work profile
4. Copy .SeedVaultAndroid to the work profile (through its Files app)
5. Restore backup from work profile setup wizard
6. Verify the app's wifi and mobile data is still blocked
Issue: calyxos#2586
Change-Id: I44da196614a749c2c8b0113cade92215e88fed4a