Add more Wi-Fi DPP UI features.

1. Update strings and icons.
2. Add more UI features in WifiDppAddDeviceFragment &
   WifiDppChooseSavedWifiNetworkFragment.

Bug: 118794978
Test: manual test
Change-Id: I2bee3f66732a1083fb13c113695899272e98c23e

src/com/android/settings/wifi/dpp/WifiDppConfiguratorActivity.java

@@ -273,7 +273,6 @@ public class WifiDppConfiguratorActivity extends InstrumentedActivity implements
     public void onScanWifiDppSuccess(String publicKey, String information) {
         mPublicKey = publicKey;
         mInformation = information;
-        mWifiNetworkConfig = null;
 
         showAddDeviceFragment(/* addToBackStack */ true);
     }