[FLINK-28992][table-planner] fix: Change Ndv takes the max value instead of sum of all partitions when getting partition table column stats

[swuferhong]

What is the purpose of the change

Now, when we obtain column statistics Ndv of the partition table, we use the method of taking sum of Ndv of all partitions, which will cause the obtained stats to be far from the real stats. So now we take the max value instead of sum of all partitions.

Brief change log

• Change Ndv takes the max value instead of sum of all partitions when getting partition table column stats.
• Modify related test.

Verifying this change

• Modify related test.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: (yes / no / don't know)
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? no

[flinkbot]

CI report:

• 01464f9 Azure: SUCCESS

Bot commands

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[swuferhong]

@flinkbot run azure

[godfreyhe]

Thanks for the contribution, I left a few comments

[godfreyhe]

Thanks for the update, LGTM