[FLINK-25538][Connectors/Kafka] Migration flink-connector-kafka from junit4 to junit5

[victor09091]

What is the purpose of the change

• [JUnit5 Migration] Module: flink-connector-kafka. *

Brief change log

• Updated simple junit 4 test packages to junit 5 test packages

Verifying this change

• This change is a trivial rework / code cleanup without any test coverage.

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)

[boring-cyborg]

Thanks for opening this pull request! Please check out our contributing guidelines. (https://flink.apache.org/contributing/how-to-contribute.html)

[MartijnVisser]

@victor09091 Can you please rebase your PR?

[morazow]

Hello @victor09091, @MartijnVisser,

Any update on this issue? Otherwise I'd happy to continue the work and finish the migration. Please let me know 👍

[MartijnVisser]

@morazow Feel free to take it over :)