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.

CRs-Fixed: 557180
Change-Id: I83d4919821cb095429ff7e73a8974d92c4df086c
(cherry picked from commit 59ec7bc7e1f29edc74512b7c180dc9559202a063)
(cherry picked from commit a1df3d0f11a974c9caa199fc7be1c47cfd809cf3)