TopicPartitionWriter should read offsets from a path with Partitioner.generatePartitionedPath

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refer to the code current PartitionWriter read offsets from a fixed topic path:
String path = FileUtils.topicDirectory(url, topicsDir, tp.topic());
the path comes to "url/topicsDir/topic"

if customed Partitioner.geratePartitionedPath do not return a path with that form, then the tp writer can not read the offset and will always start with offset 0...

Thanks.

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releated to pr191:
#191