Add dump log for BatteryTip.

Since BatteryTipLoader will dump all BatteryTips, so we only need
to add toString() for it.

Bug: 74246970
Test: RunSettingsRoboTests
Change-Id: I0a89c4ac06d107274d47f8b4b66867373c062c1b

src/com/android/settings/fuelgauge/batterytip/tips/BatteryTip.java

@@ -158,4 +158,9 @@ public abstract class BatteryTip implements Comparable<BatteryTip>, Parcelable {
     public int compareTo(BatteryTip o) {
         return TIP_ORDER.get(mType) - TIP_ORDER.get(o.mType);
     }
+
+    @Override
+    public String toString() {
+        return "type=" + mType + " state=" + mState;
+    }
 }