add iceberg support

[zhangjun0x01]

Iceberg is a popular data lake framework. I think we should add iceberg as the data source of alink.

At present, I add alink to read iceberg without add write operations, because their APIs are incompatible. Flick realizes the integration of batch and stream. Iceberg also uses Datastream to realize batch and stream processing. However, at present, alink uses Dataset for batch processing, so I don't find a good way to be compatible at the moment.

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