Bluetooth: Only show devices when their names are resolved

* Add a developer menu option to allow name-less devices to be shown
  when a Bluetooth developer needs it, but hide it for non-developer
  users.
* Set BluetoothDevicePreference to invisible when CachedBluetoothDevice
  does not have a name besides MAC address and the above developer option
  is false.
* This affects BluetoothPairingDetail and DevicePickerFragment, but does
  not affect BluetoothSettings. BluetoothSettings will show all paired
  devices regardless whether an user friendly name exists.

Bug: 34685932
Test: pair Bluetooth device, send file over Bluetooth, unit tests
Change-Id: Idd7ad4b1671dfdcf3204efb50eddb6dae1065aa5

src/com/android/settings/bluetooth/BluetoothSettings.java

@@ -140,6 +140,8 @@ public class BluetoothSettings extends DeviceListPreferenceFragment implements I
             mBluetoothEnabler.resume(getActivity());
         }
         super.onStart();
+        // Always show paired devices regardless whether user-friendly name exists
+        mShowDevicesWithoutNames = true;
         if (isUiRestricted()) {
             getPreferenceScreen().removeAll();
             if (!isUiRestrictedByOnlyAdmin()) {