[SPARK-22721] BytesToBytesMap peak memory not updated.

## What changes were proposed in this pull request?

Follow-up to earlier commit.
The peak memory of BytesToBytesMap is not updated in more places - spill() and destructiveIterator().

## How was this patch tested?

Manually.

Author: Juliusz Sompolski <[email protected]>

Closes #19923 from juliuszsompolski/SPARK-22721cd.

Author: juliuszsompolski

core/src/main/java/org/apache/spark/unsafe/map/BytesToBytesMap.java

@@ -347,6 +347,8 @@ public long spill(long numBytes) throws IOException {
           return 0L;
         }
 
+        updatePeakMemoryUsed();
+
         // TODO: use existing ShuffleWriteMetrics
         ShuffleWriteMetrics writeMetrics = new ShuffleWriteMetrics();
 
@@ -424,6 +426,7 @@ public MapIterator iterator() {
    * `lookup()`, the behavior of the returned iterator is undefined.
    */
   public MapIterator destructiveIterator() {
+    updatePeakMemoryUsed();
     return new MapIterator(numValues, loc, true);
   }