Add feature flag for new DataUsageSummary fragment.

Creates a new fragment DataUsageSummaryLegacy, which is used
instead of DataUsageSummary when the feature flag is off (default
behavior).

Copies the current DataUsageSummary.java, data_usage.xml, and
DataUsageSummaryActivity to create the legacy versions. This
change allows for uninterupted development of new features in the
DataUsageSummary fragment.

Test: manual
Test: make RunSettingsRoboTests
Bug: 70950124
Change-Id: I9d79e108bbfc1c8ec620f86c0183f4ed3f41c9d7

src/com/android/settings/core/FeatureFlags.java

@@ -26,4 +26,5 @@ public class FeatureFlags {
     public static final String ZONE_PICKER_V2 = "settings_zone_picker_v2";
     public static final String ABOUT_PHONE_V2 = "settings_about_phone_v2";
     public static final String BLUETOOTH_WHILE_DRIVING = "settings_bluetooth_while_driving";
+    public static final String DATA_USAGE_SETTINGS_V2 = "settings_data_usage_v2";
 }

src/com/android/settings/core/gateway/SettingsGateway.java

@@ -62,6 +62,7 @@ import com.android.settings.connecteddevice.usb.UsbDetailsFragment;
 import com.android.settings.datausage.DataPlanUsageSummary;
 import com.android.settings.datausage.DataUsageList;
 import com.android.settings.datausage.DataUsageSummary;
+import com.android.settings.datausage.DataUsageSummaryLegacy;
 import com.android.settings.deletionhelper.AutomaticStorageManagerSettings;
 import com.android.settings.development.DevelopmentSettingsDashboardFragment;
 import com.android.settings.deviceinfo.DeviceInfoSettings;
@@ -189,6 +190,7 @@ public class SettingsGateway {
             CryptKeeperSettings.class.getName(),
             DataPlanUsageSummary.class.getName(),
             DataUsageSummary.class.getName(),
+            DataUsageSummaryLegacy.class.getName(),
             DreamSettings.class.getName(),
             UserSettings.class.getName(),
             NotificationAccessSettings.class.getName(),