Add hidden API to get current user of HID Device (2/3)

Bug: 69136526
Test: test with apps using HID Device profile
Change-Id: I6c6df052fac508499c42fc7ab493010e327d6003

system/binder/android/bluetooth/IBluetoothHidDevice.aidl

@@ -36,4 +36,5 @@ interface IBluetoothHidDevice {
     List<BluetoothDevice> getConnectedDevices();
     List<BluetoothDevice> getDevicesMatchingConnectionStates(in int[] states);
     int getConnectionState(in BluetoothDevice device);
+    String getUserAppName();
 }