Pretend to be Settings for location notifications

This looks up the Settings app name via the public activity
intent and adds that to the notification header.

Also requires we request the SUBSTITUTE_NOTIFICATION_APP_NAME
permission.

Bug: 128608303
Test: trigger notification, look at sender app ('Settings' on a Google build)
Change-Id: Idb52ca36c837f6a012a2e13fe380f107f7a70130