[FLINK-36968][table-planner] Deduplicate data with the same pk in values lookup table used for testing

[xuyangzhong]

What is the purpose of the change

This pr tries to fix the 'values' connector only used for testing!
Currently, the "values" lookup table used for testing does not deduplicate data with the same pk.

Brief change log

• Deduplicate the data with same pk in values lookup table
• Add tests

Verifying this change

A test is added to verify this fix.

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?

[flinkbot]

CI report:

• e13c348 Azure: SUCCESS

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