[SPARK-48391][CORE] Using addAll instead of add function in fromAccum…

…ulatorInfos method of TaskMetrics Class

### What changes were proposed in this pull request?

Using addAll instead of add function in fromAccumulators method of TaskMetrics.

### Why are the changes needed?

To Improve performance. In the fromAccumulators method of TaskMetrics，we should use `
tm._externalAccums.addAll` instead of `tm._externalAccums.add`, as _externalAccums is a instance of CopyOnWriteArrayList

### Does this PR introduce _any_ user-facing change?

yes.

### How was this patch tested?

No Tests.

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes apache#46705 from monkeyboy123/fromAccumulators-accelerate.

Authored-by: Dereck Li <monkeyboy.ljh@gmail.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>

core/src/main/scala/org/apache/spark/executor/TaskMetrics.scala

@@ -328,16 +328,19 @@ private[spark] object TaskMetrics extends Logging {
    */
   def fromAccumulators(accums: Seq[AccumulatorV2[_, _]]): TaskMetrics = {
     val tm = new TaskMetrics
+    val externalAccums = new java.util.ArrayList[AccumulatorV2[Any, Any]]()
     for (acc <- accums) {
       val name = acc.name
+      val tmpAcc = acc.asInstanceOf[AccumulatorV2[Any, Any]]
       if (name.isDefined && tm.nameToAccums.contains(name.get)) {
         val tmAcc = tm.nameToAccums(name.get).asInstanceOf[AccumulatorV2[Any, Any]]
         tmAcc.metadata = acc.metadata
-        tmAcc.merge(acc.asInstanceOf[AccumulatorV2[Any, Any]])
+        tmAcc.merge(tmpAcc)
       } else {
-        tm._externalAccums.add(acc)
+        externalAccums.add(tmpAcc)
       }
     }
+    tm._externalAccums.addAll(externalAccums)
     tm
   }
 }