Update UI for Wifi Direct settings

- Change the launching preference from using an intent to directly a
fragemnt
- Partially convert WifiP2pSettings to a DashboardFragment
- Add a controller to control each pref category, when they have no
child, hide.
- Add a controller to control device's own AP name.

Change-Id: I23685c4d4a85f80ceab5a576005e693e6f8b7cc4
Fix: 36859626
Test: make RunSettingsRoboTests

res/xml/wifi_p2p_settings.xml

@@ -15,5 +15,13 @@
 -->
 
 <PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
-
+    <Preference
+        android:key="p2p_this_device"
+        android:selectable="false" />
+    <PreferenceCategory
+        android:key="p2p_peer_devices"
+        android:title="@string/wifi_p2p_peer_devices" />
+    <PreferenceCategory
+        android:key="p2p_persistent_group"
+        android:title="@string/wifi_p2p_remembered_groups" />
 </PreferenceScreen>