Move preferences to Notification page

Based on the Android S design,
- Fork configure_notification_settings_v2 for dev.
- Move "Conversations" from Apps to Notification above "Bubbles".
- Move "Wireless emergency alerts" from Apps to Notifications.

Bug: 174964405
Test: robotest & visual with turning on/off silky home

Change-Id: Ib8e19956ed7717924423eb632d4546314a34d549