perf(log): increase FETCH_BATCH_SIZE to 512KB in StreamSegmentInputStream (#2722)

Author: Gezi-lzq

core/src/main/scala/kafka/log/streamaspect/ElasticLogFileRecords.java

@@ -408,7 +408,7 @@ public long lastOffset() {
 
     static class StreamSegmentInputStream implements LogInputStream<RecordBatch> {
         @VisibleForTesting
-        protected static final int FETCH_BATCH_SIZE = 64 * 1024;
+        protected static final int FETCH_BATCH_SIZE = 512 * 1024;
         private final ElasticLogFileRecords elasticLogFileRecords;
         private final Queue<RecordBatch> remaining = new LinkedList<>();
         private final int maxSize;