HFP: Add isInbandRingingEnabled() API (3/4)

* Use BluetoothHeadset.isInbandRingingEnabled() API to check whether
  in-band ringing is currently enabled in the system when deciding on
  audio routes for ringtone
* Use this value obtained in Java layer to initialize native HFP/HSP
  stack instead of checking it in native layer

Bug: 71646213
Test: make, toggle in-band ringing from Development Settings and observe
      whether Telecom service tries to open SCO when there is an
      incoming call

Change-Id: I917537b6d17681151639ff29a56ac9c0c7e0e7e8