Update App battery usage page and add tests.

- Add tests
- Remove duplicated "Set battery usage for apps" text
- Clean up some code

Screenshot: https://screenshot.googleplex.com/8LHhyxFA6X4ZFkT.png

Test: make RunSettingsRoboTests -j40
Bug: 244995036
Change-Id: Iaac9b0af10f541100e91b10affacf3307bd5edca

src/com/android/settings/applications/manageapplications/ManageApplications.java

@@ -1196,9 +1196,12 @@ public class ManageApplications extends InstrumentedFragment
                     rebuild(R.id.sort_order_alpha, true);
                 }
                 return;
-            } else if (mManageApplications.mListType == LIST_TYPE_BATTERY_OPTIMIZATION) {
+            }
+
+            if (mManageApplications.mListType == LIST_TYPE_BATTERY_OPTIMIZATION) {
                 logAppBatteryUsage(filterType);
             }
+
             rebuild();
         }
 
@@ -1673,7 +1676,7 @@ public class ManageApplications extends InstrumentedFragment
                     holder.setSummary(AppLocaleDetails.getSummary(mContext, entry));
                     break;
                 case LIST_TYPE_BATTERY_OPTIMIZATION:
-                    holder.setSummary(R.string.app_battery_usage_summary);
+                    holder.setSummary(null);
                     break;
                 default:
                     holder.updateSizeText(entry, mManageApplications.mInvalidSizeStr, mWhichSize);