Add ability to show/hide Wi-Fi settings, and all related sub-settings.

This adds a new boolean flag, config_show_wifi_settings, which when set
to false will hide the "Wi-Fi" page in network & internet (there is no
key value associated with this preference page). It will also hide
nested pages from search results, such as Wi-Fi preferences.

Bug: 62379554
Test: make RunSettingsRoboTests
ROBOTEST_FILTER=ConfigureWifiSettingsTest
and
make RunSettingsRoboTests
ROBOTEST_FILTER=WifiSettingsTest
and
make RunSettingsRoboTests
ROBOTEST_FILTER=WifiMasterSwitchPreferenceControllerTest
all pass.

Change-Id: Iedc6bc272e0cb2b561c6bf25968e70f355aaaa8e

tests/robotests/src/com/android/settings/wifi/ConfigureWifiSettingsTest.java

@@ -44,6 +44,17 @@ public class ConfigureWifiSettingsTest {
         assertThat(keys).containsAllIn(niks);
     }
 
+    @Test
+    @Config(qualifiers = "mcc999")
+    public void testNonIndexableKeys_ifPageDisabled_shouldNotIndexResource() {
+        final List<String> niks = ConfigureWifiSettings.SEARCH_INDEX_DATA_PROVIDER
+                .getNonIndexableKeys(mContext);
+        final int xmlId = new ConfigureWifiSettings().getPreferenceScreenResId();
+
+        final List<String> keys = XmlTestUtils.getKeysFromPreferenceXml(mContext, xmlId);
+        assertThat(niks).containsAllIn(keys);
+    }
+
     @Test
     public void testNonIndexableKeys_noConnection_blocksIP() {
         ConnectivityManager manager = mock(ConnectivityManager.class);