Add resources for after call spam notification.

+Block icon from https://icons.googleplex.com/#icon=ic_block
+Person add icon from https://icons.googleplex.com/#icon=ic_person_add
+X icon from https://icons.googleplex.com/#icon=ic_close
+Report icon from https://icons.googleplex.com/#icon=ic_report
+Question mark icon from @ycnzhao
+Added spam_notification_icon for the large icon in notifications for
first time spam calls
+Added unknown_notification_icon for the large icon in notifications for
first time calls (from any number)
+Added strings for after call notifications
+This is the same as ag/919969, we decided to move the after call spam
notification stuff to the AOSP dialer

BUG=27323295

Change-Id: I0aaabd8d2dbefeda5214481ce6315335e64c3c28