Make app predicates singleton

1. AppLabelPredicate
2. AppRestrictionPredicate

Change-Id: I1fd8611c5dd7ffa6318bcb23de7a973c111910b6
Fixes: 111323520
Test: RunSettingsRoboTests

tests/robotests/src/com/android/settings/testutils/BatteryTestUtils.java

@@ -19,6 +19,8 @@ package com.android.settings.testutils;
 import android.content.Intent;
 import android.os.BatteryManager;
 
+import java.lang.reflect.Field;
+
 public class BatteryTestUtils {
 
     public static Intent getChargingIntent() {
@@ -47,4 +49,15 @@ public class BatteryTestUtils {
         return intent;
     }
 
+    public static void clearStaticInstance(Class clazz, String fieldName) {
+        Field instance;
+        try {
+            instance = clazz.getDeclaredField(fieldName);
+            instance.setAccessible(true);
+            instance.set(null, null);
+        } catch (Exception e) {
+            throw new RuntimeException();
+        }
+    }
+
 }