Allow user to disable network boost notification

CarrierDefaultApp notification channels are not able to be disabled by
default. Allow the network boost channel notifications to be blockable
so user can disable them without affecting other notificatons in
CarrierDefaultApp.

Test: manual test
Bug: 258266536
Change-Id: I8907205e905b9fbdab3193f1816074b9ed62e785
2 files changed