Use alternative PhoneStateListener formal API

ConnectivityService is going to become a mainline module which
will not able to access hidden APIs. Replace with alternative
constructor with an executor.

Bug: 171183530
Test: atest FrameworksNetTests
Test: manually test to check if phone states notify correctly
Change-Id: Iebd1f45384570bb9ba6be8041dd17310f7b025d3