Use BatterySaverReceiver in battery saver settings

Use this receiver to listen to following updates:
1. Plug state: if it is plugged in, disable this two state
button, otherwise make it enabled
2. low power mode: If mode on, show "turn off" otherwise show
"turn on"

Bug: 72228477
Test: RunSettingsRoboTests
Change-Id: Ib3d3df9f9a5fbac8b1b876c9e193beb75f522ebd

src/com/android/settings/widget/TwoStateButtonPreferenceController.java

@@ -47,7 +47,7 @@ public abstract class TwoStateButtonPreferenceController extends BasePreferenceC
         mButtonOff.setOnClickListener(this);
     }
 
-    protected void updateButton(boolean stateOn) {
+    protected void setButtonVisibility(boolean stateOn) {
         if (stateOn) {
             mButtonOff.setVisibility(View.GONE);
             mButtonOn.setVisibility(View.VISIBLE);
@@ -57,6 +57,11 @@ public abstract class TwoStateButtonPreferenceController extends BasePreferenceC
         }
     }
 
+    protected void setButtonEnabled(boolean enabled) {
+        mButtonOn.setEnabled(enabled);
+        mButtonOff.setEnabled(enabled);
+    }
+
     @Override
     public void onClick(View v) {
         final boolean stateOn = v.getId() == R.id.state_on_button;