[Feature Request]: Use `partitionsFor` instead of `listTopics` in `ReadFromKafkaDoFn`

[dartiga]

What would you like to happen?

For brokers with a huge amount of partitions, using listTopics adds unnecessary overhead. Using partitionsFor would be preferable.

Issue Priority

Priority: 2 (default / most feature requests should be filed as P2)

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[dartiga]

So instead of

for (List<PartitionInfo> topicPartitionList : consumer.listTopics().values()) {
    topicPartitionList.forEach(
        partitionInfo -> {
          existingTopicPartitions.add(
              new TopicPartition(partitionInfo.topic(), partitionInfo.partition()));
        });
}

Have something like:

List<PartitionInfo> topicPartitionList =
          consumer.partitionsFor(kafkaSourceDescriptor.getTopicPartition().topic());
topicPartitionList.forEach(
    partitionInfo -> {
         existingTopicPartitions.add(
              new TopicPartition(partitionInfo.topic(), partitionInfo.partition()));
    });