add app battery optimization settings link to Battery screen

res/xml/power_usage_summary.xml

@@ -81,6 +81,11 @@
             settings:controller="com.google.android.settings.fuelgauge.reversecharging.ReverseChargingPreferenceController" />
     </PreferenceCategory>
 
+    <Preference
+        android:key="app_battery_usage"
+        android:title="@string/app_battery_usage_title"
+        settings:controller="com.android.settings.fuelgauge.AppBatteryUsagePrefController" />
+
     <!-- Charging control -->
     <lineageos.preference.LineagePartsPreference
         android:key="charging_control"

src/com/android/settings/fuelgauge/AppBatteryUsagePrefController.java

@@ -0,0 +1,32 @@
+package com.android.settings.fuelgauge;
+
+import android.content.Context;
+import android.text.TextUtils;
+
+import androidx.preference.Preference;
+
+import com.android.settings.core.BasePreferenceController;
+import com.android.settings.spa.SpaActivity;
+import com.android.settings.spa.app.battery.BatteryOptimizationModeAppListPageProvider;
+
+public class AppBatteryUsagePrefController extends BasePreferenceController {
+
+    public AppBatteryUsagePrefController(Context context, String key) {
+        super(context, key);
+    }
+
+    @Override
+    public int getAvailabilityStatus() {
+        return AVAILABLE;
+    }
+
+    @Override
+    public boolean handlePreferenceTreeClick(Preference preference) {
+        if (!TextUtils.equals(preference.getKey(), getPreferenceKey())) {
+            return false;
+        }
+
+        SpaActivity.startSpaActivity(mContext, BatteryOptimizationModeAppListPageProvider.INSTANCE.getName());
+        return true;
+    }
+}