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
diff --git a/src/com/android/settings/Settings.java b/src/com/android/settings/Settings.java
index 741bfda..b962672 100644
--- a/src/com/android/settings/Settings.java
+++ b/src/com/android/settings/Settings.java
@@ -80,6 +80,7 @@
     public static class DeviceAdminSettingsActivity extends SettingsActivity { /* empty */ }
     public static class DataPlanUsageSummaryActivity extends SettingsActivity { /* empty */ }
     public static class DataUsageSummaryActivity extends SettingsActivity { /* empty */ }
+    public static class DataUsageSummaryLegacyActivity extends SettingsActivity { /* empty */ }
     public static class MobileDataUsageListActivity extends SettingsActivity { /* empty */ }
     public static class ConfigureWifiSettingsActivity extends SettingsActivity { /* empty */ }
     public static class SavedAccessPointsSettingsActivity extends SettingsActivity { /* empty */ }