Bluetooth: DUN: Add DUN profile support in Settings APP

It registers service listener for DUN profile with the
BT adapter, and it will track the profile status with
the service listener state chnages.

It also has support for DUN profile connection status
updation and DUN Disconnection from server.

Change-Id: I83d4919821cb095429ff7e73a8974d92c4df086c

Change-Id: I83d4919821cb095429ff7e73a8974d92c4df086c