Remove redundant methods and refactor

Remove the summary method and write the code in AOSP directly instead to
force string consistency. Also refactor a bit after the modification.

Fixes: 276399056
Test: robotests
Change-Id: I76ad740b694363a3cdfb3748e41c840fb678b93d

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

@@ -64,8 +64,10 @@ import com.google.protobuf.MessageLite;
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
-import java.time.Duration;
 import java.time.Instant;
+import java.time.ZoneId;
+import java.time.format.DateTimeFormatter;
+import java.time.format.FormatStyle;
 import java.util.List;
 
 /**
@@ -671,6 +673,14 @@ public class BatteryUtils {
         }
         return summary.toString();
     }
+    /** Format the date of battery related info */
+    public static CharSequence getBatteryInfoFormattedDate(long dateInMs) {
+        final Instant instant = Instant.ofEpochMilli(dateInMs);
+        final String localDate = instant.atZone(ZoneId.systemDefault()).toLocalDate().format(
+                DateTimeFormatter.ofLocalizedDate(FormatStyle.LONG));
+
+        return localDate;
+    }
 
     /** Builds the battery usage time information for one timestamp. */
     private static String buildBatteryUsageTimeInfo(final Context context, long timeInMs,