Add restore metrics for settings that use the restoreSettings() method.

Adds metrics logging for restored settings that are queried from the db. That is: system, global, secure and device_specific_config.

This is part of an effort to add metrics support to SettingsBackupAgent. For more details, see go/settings-backup-agent-metrics-design

Bug: 379861078
Change-Id: Ie5f2fb43f0c89c790de7ba4a089a0db11c99ebdf
Flag: com.android.server.backup.enable_metrics_settings_backup_agents
Tested: SettingsBackupAgentTest and manually by verifying that the metrics are logged in the dumpsys (https://screenshot.googleplex.com/7tKexN3cmFjiycC)