Improvement for BatchMessagingMessageConverter.toMessage()

While analyzing the toMessage() function of BatchMessagingMessageConverter, improvements were made. We have worked on improving it accordingly.

1. Replace traditional loops with Java Stream API for processing collections. This enhances code conciseness and readability, allowing for functional-style operations on data.

private void processRecord(ConsumerRecord<?, ?> record, List<Object> payloads, List<Object> keys,
			List<String> topics, List<Integer> partitions, List<Long> offsets,
			List<String> timestampTypes, List<Long> timestamps, List<Map<String, Object>> convertedHeaders,
			List<Headers> natives, List<ConsumerRecord<?, ?>> raws, List<ConversionException> conversionFailures,
			Map<String, Object> rawHeaders, Type type) {
  // proceedRecord..
}

2. Utilize Optional to handle potential null values more gracefully.
3. Separate function that prints log once

I think The analysis of the toMessage() code is expected to become more convenient.