NIFI-5928 Use NiFiDataPacket in the Flink source

[ambition119]

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[ambition119]

@rwhittington @pvillard31 Could you help review this PR?

[bbende]

@ambition119 currently the flink nifi connectors are part of flink, so shouldn't this PR be against the flink repo?

https://github.com/apache/flink/tree/master/flink-connectors/flink-connector-nifi

[ambition119]

@ambition119 currently the flink nifi connectors are part of flink, so shouldn't this PR be against the flink repo?

https://github.com/apache/flink/tree/master/flink-connectors/flink-connector-nifi

ok