Set Wi-Fi DPP fragment icons.

1. set fragment icon for WifiDppChooseSavedWifiNetworkFragment
2. set fragment icon of success for WifiDppAddDeviceFragment

All Wi-Fi DPP fragment icons are VectorDrawable of instinct size
24dp draw on a 48dp canvas. Except for ic_devices_check_circle_green,
it's a LayerDrawable of different size. I dynamically change ImageView
layout width & height between these 2 different kind of drawable.

Bug: 122982132
Test: manual test
Change-Id: Idab8cd8b0798363e447da00dc6bc68a86498b8be

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

@@ -171,7 +171,7 @@ public class WifiDppQrCodeScannerFragment extends WifiDppQrCodeBaseFragment impl
 
         mDecorateView = (QrDecorateView) view.findViewById(R.id.decorate_view);
 
-        mHeaderIcon.setImageResource(R.drawable.ic_scan_24dp);
+        setHeaderIconImageResource(R.drawable.ic_scan_24dp);
         if (mIsConfiguratorMode) {
             mTitle.setText(R.string.wifi_dpp_add_device_to_network);