[FLINK-40304][table] Fix PTF partition columns for multiple table arguments

[Au-Miner]

What is the purpose of the change

This change fixes incorrect partition-column positions inferred for a PTF with multiple table arguments. The bug can omit an upsert key from a later table argument and prevent a valid query from being planned for an upsert sink.

Brief change log

• Correct StreamPhysicalProcessTableFunction#toPartitionColumns to account for the cumulative output offset when deriving partition columns.
• Add a regression plan test whose sink primary key corresponds to the partition column of the second table argument.

Verifying this change

Added ProcessTableFunctionTest#testUpsertKeyWithMultipleTableArgs to verify that the partition column of the second table argument remains a valid upsert key. The targeted regression test and the complete ProcessTableFunctionTest suite with 69 tests passed.

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? not applicable

[flinkbot]

CI report:

• 26e3d84 Azure: SUCCESS

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