Support merge chunkInfos in client

The chunk size of the streaming is usually smaller than 4MB, we suggest set to 512KB for better performance. In this case, files of the same size will generate more chunkInfo than async write, which increases the size of container DB. So we recommend add merge on the client side. The default value is 0, means merge is not enabled. If the value is 8, it means that every 8 chunkInfo will be merged to one.