check immediately for updates if user enables 'check for updates setting'

- Convert CheckForNewAppVersion to IntentService
- reset expire date to 0 after user enables check for updates setting

app/src/main/AndroidManifest.xml

@@ -358,6 +358,9 @@
         <service
             android:name=".RouterActivity$FetcherService"
             android:exported="false" />
+        <service
+            android:name=".CheckForNewAppVersion"
+            android:exported="false" />
 
         <!-- opting out of sending metrics to Google in Android System WebView -->
         <meta-data android:name="android.webkit.WebView.MetricsOptOut" android:value="true" />