Use SettingsLib's MainSwitchBar to replace SwitchBar in Settings.

To log Settings metrics, the MainSwitch extends MainSwitchBar and
replace the SwitchBar in SettingsActivity.

Bug: 175181773
Test: Run robotest and apply the widget in Settings and see the ui

Change-Id: I3add3702e9058ad9192b5172c7cf0e2ccfb55a70

src/com/android/settings/bluetooth/BluetoothEnabler.java

@@ -75,6 +75,8 @@ public final class BluetoothEnabler implements SwitchWidgetController.OnSwitchCh
         mMetricsFeatureProvider = metricsFeatureProvider;
         mSwitchController = switchController;
         mSwitchController.setListener(this);
+        mSwitchController.setTitle(context.getString(R.string.bluetooth_main_switch_title));
+
         mValidListener = false;
         mMetricsEvent = metricsEvent;
 
@@ -191,7 +193,6 @@ public final class BluetoothEnabler implements SwitchWidgetController.OnSwitchCh
             if (isChecked && !status) {
                 mSwitchController.setChecked(false);
                 mSwitchController.setEnabled(true);
-                mSwitchController.updateTitle(false);
                 triggerParentPreferenceCallback(false);
                 return false;
             }