Add "Sensitive Content" public view

This view, used when sensitive content is detected, and the standard
public view does not apply, keeps the notificaiton title and icon, but
replaces the notification content.

Test: atest
Flag: android.app.redact_sensitive_content_notifications_on_lockscreen
NotificationContentInflaterTest,NotificationRowContentBinderImplTest
Bug: 358403414

Change-Id: I8da06736284a3c3d551f2bea0332b4cc32eccf6e