Bluetooth: Tracking the devices added using BLE On Apps

This change keeps a hashset of the devices connected using BLE Always
On Apps, so that when ACL disconnection callbacks are received in
STATE_BLE_ON or BLE_TURNING_OFF, the BLE_ACL_DISCONNECTED broadcast
is sent to only those ACL connections wheras the other devices
disconnecting due to reasons such as BT turn Off or SSR can still
receive ACL_DISCONNECTED intents.

Change-Id: I19b0f257d53f9d0e5590316b06088852ccd32804