[FLINK-29059][table-planner] Fix the existing column stats are deleted incorrectly when analyze table for partial columns

[swuferhong]

What is the purpose of the change

If there are three columns named a, b, c with column stats already exists for non partition table, when user just analyze column a using Analyze table xxx FOR COLUMNS a, the existing column stats of b, c will be reset back to empty. This error also exists for the partition table.

Brief change log

• Adding the operation of merging column statistics in AnalyzeTableUtil.
• Adding tests to cover this condition.

Verifying this change

• IT test is added in AnalyzeTableITCase to cover this condition.

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: no
• 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 docs.

[flinkbot]

CI report:

• 97ae1a3 Azure: SUCCESS

Bot commands

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• @flinkbot run azure re-run the last Azure build

[godfreyhe]

LGTM overall, except one minor comment