Add preference for device suggestions

This preference links to an external screen where users can configure
the device suggestions feature on their device. The content of the
preference and the settings page must be set by a system app.

NO_IFTTT=no need to update MediaControlsSettings

Flag: com.android.settings.flags.device_suggestions_preference
Test: local test
Bug: 415096359
Change-Id: I4bc038dbfcd432de9b90d2a9aa29487a17390f8c