Use Kotlin List & NonNull String

To avoid Room compiler error / warning.

Bug: 332487783
Test: m Settings
Flag: EXEMPT refactor
Change-Id: I79a4991c1a0009e347f0916f4f204229dc07581a

src/com/android/settings/fuelgauge/batteryusage/db/BatteryReattributeDao.kt

@@ -21,11 +21,9 @@ import androidx.room.Insert;
 import androidx.room.OnConflictStrategy;
 import androidx.room.Query;
 
-import java.util.List;
-
 /** DAO for accessing {@link BatteryReattributeEntity} in the database. */
 @Dao
-public interface BatteryReattributeDao {
+interface BatteryReattributeDao {
 
     /** Inserts a {@link BatteryReattributeEntity} data into the database. */
     @Insert(onConflict = OnConflictStrategy.REPLACE)

src/com/android/settings/fuelgauge/batteryusage/db/BatteryReattributeEntity.java

@@ -18,14 +18,14 @@ package com.android.settings.fuelgauge.batteryusage.db;
 
 import static com.android.settings.fuelgauge.batteryusage.ConvertUtils.utcToLocalTimeForLogging;
 
-import com.android.settings.fuelgauge.batteryusage.BatteryReattribute;
-import com.android.settings.fuelgauge.batteryusage.ConvertUtils;
-
 import androidx.annotation.NonNull;
 import androidx.annotation.VisibleForTesting;
 import androidx.room.Entity;
 import androidx.room.PrimaryKey;
 
+import com.android.settings.fuelgauge.batteryusage.BatteryReattribute;
+import com.android.settings.fuelgauge.batteryusage.ConvertUtils;
+
 /** A {@link Entity} for battery usage reattribution data in the database. */
 @Entity
 public class BatteryReattributeEntity {
@@ -38,7 +38,7 @@ public class BatteryReattributeEntity {
     public final long timestampEnd;
 
     /** The battery usage reattribution data for corresponding  uids. */
-    public final String reattributeData;
+    @NonNull public final String reattributeData;
 
     public BatteryReattributeEntity(@NonNull BatteryReattribute batteryReattribute) {
         this(