Use feature flag to show/hide AllInOneTetherSettings

This partially reverts commit 0ccc849de7
which added a config value. Instead, we will use feature flag to switch
between the fragments.

This CL also adds a postfix to keys in all_tether_prefs to
de-duplicate with keys in tether_prefs and wifi_tether_settings.

Bug: 148182953
Change-Id: I92832c786473990065a965409072e4117a7e75a8
Fix: 148618984
Test: make RunSettingsRoboTests
Test: make RunSettingsRoboTests ROBOTEST_FILTER=CodeInspectionTest

src/com/android/settings/wifi/tether/WifiTetherSettings.java

@@ -28,6 +28,7 @@ import android.net.wifi.SoftApConfiguration;
 import android.net.wifi.WifiManager;
 import android.os.Bundle;
 import android.os.UserManager;
+import android.util.FeatureFlagUtils;
 import android.util.Log;
 
 import androidx.annotation.VisibleForTesting;
@@ -35,6 +36,7 @@ import androidx.preference.PreferenceGroup;
 
 import com.android.settings.R;
 import com.android.settings.SettingsActivity;
+import com.android.settings.core.FeatureFlags;
 import com.android.settings.dashboard.RestrictedDashboardFragment;
 import com.android.settings.search.BaseSearchIndexProvider;
 import com.android.settings.widget.SwitchBar;
@@ -259,8 +261,7 @@ public class WifiTetherSettings extends RestrictedDashboardFragment
 
                 @Override
                 protected boolean isPageSearchEnabled(Context context) {
-                    return !context.getResources().getBoolean(
-                            R.bool.config_show_all_in_one_tether_settings);
+                    return !FeatureFlagUtils.isEnabled(context, FeatureFlags.TETHER_ALL_IN_ONE);
                 }
 
                 @Override