[FLINK-23971][tests] fix connector testing framework error when compare records in different splits

[ruanhang1993]

What is the purpose of the change

This pull request resolves the error in the connector testing framework, when comparing the result with data in different splits. When achieving your own ExternalContext, the records in different splits returned by method generateTestData should be judged not as equal by method equlas.

Brief change log

• add the splitIndex parameter to the method generateTestData
• modify the tests and the implements for ExternalContext, make sure generated records in different splits by generateTestData be judged not as equal

Verifying this change

This change is already covered by existing tests

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)

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Automated Checks

Last check on commit 2469730 (Mon Aug 30 11:25:40 UTC 2021)

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CI report:

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[ruanhang1993]

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[ruanhang1993]

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[becketqin]

@ruanhang1993 Thanks for the patch. LGTM.

[becketqin]

Merged to master: ad052cc