Revert "Revert "Convert BT preference to use TwoTargetPreference""

This reverts commit 457c3cbec2.

Revert with fix/test.
The fix is that we removed DevicePickerFragment#initDevicePreference(),
which incorrectly set a useless widget on preference, and removes the
gear icon from preference, preventing bind() call to go through

Change-Id: Ia70cdb51d13cca6035a4e7fe8008d195f7f00c6e
Fix: 36511169
Test: runtest --path tests/app/src/com/android/settings/bluetooth/DevicePickerActivityTest.java

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

@@ -61,11 +61,6 @@ public final class DevicePickerFragment extends DeviceListPreferenceFragment {
         mLaunchClass = intent.getStringExtra(BluetoothDevicePicker.EXTRA_LAUNCH_CLASS);
     }
 
-    @Override
-    void initDevicePreference(BluetoothDevicePreference preference) {
-        preference.setWidgetLayoutResource(R.layout.preference_empty_list);
-    }
-
     @Override
     public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
         menu.add(Menu.NONE, MENU_ID_REFRESH, 0, R.string.bluetooth_search_for_devices)