Add support for per-package policy for sending premium SMS.

The default behavior for sending a message to a premium SMS
short code (or suspected premium SMS number) is to ask the user for
confirmation. Enable the user to set a default policy ("remember this
choice" checkbox) to always/never allow the app to send SMS to
premium short codes in the future. The policy can be changed by
the Settings app in the app info screen.

Bug: 5513975
Change-Id: I82731bbc6631ac79b1b5d1d9b1f96c7100ab20cf