Fix unknown exception caused by thread safety issue (#2033)

### Motivation
Both the response thread and timeout detection thread will access
PendingProduceCallback
This problem will easily occur when the sending latency is close to the
timeout threshold.

Step-1： response thread and timeout detection thread access 1 at the
same time, none of them meet the conditions for return

Step-2: timeout detection thread execute to 2, and set responseMap =
null
Setp-3: response thread execute to 3,  cause NPE

<img width="864" alt="image"
src="https://github.com/streamnative/kop/assets/9758905/96a1a8f5-cf09-4bcd-8f4a-24f9c8205474">


### Modifications
Add synchronized

kafka-impl/src/main/java/io/streamnative/pulsar/handlers/kop/storage/ReplicaManager.java

@@ -108,17 +108,18 @@ private static class PendingProduceCallback implements Runnable {
         final CompletableFuture<Map<TopicPartition, ProduceResponse.PartitionResponse>> completableFuture;
         Map<TopicPartition, MemoryRecords> entriesPerPartition;
         @Override
-        public void run() {
+        public synchronized void run() {
             topicPartitionNum.set(0);
             if (completableFuture.isDone()) {
                 // It may be triggered again in DelayedProduceAndFetch
                 return;
             }
             // add the topicPartition with timeout error if it's not existed in responseMap
             entriesPerPartition.keySet().forEach(topicPartition -> {
-                if (!responseMap.containsKey(topicPartition)) {
+                ProduceResponse.PartitionResponse response = responseMap.putIfAbsent(topicPartition,
+                        new ProduceResponse.PartitionResponse(Errors.REQUEST_TIMED_OUT));
+                if (response == null) {
                     log.error("Adding dummy REQUEST_TIMED_OUT to produce response for {}", topicPartition);
-                    responseMap.put(topicPartition, new ProduceResponse.PartitionResponse(Errors.REQUEST_TIMED_OUT));
                 }
             });
             if (log.isDebugEnabled()) {