[FLINK-23120][python] Fix ByteArrayWrapperSerializer.serialize to use writeInt to serialize the length

[dianfu]

What is the purpose of the change

This pull request fixes ByteArrayWrapperSerializer

Verifying this change

This change added tests and can be verified as follows:

• Added tests ByteArrayWrapperSerializerTest

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/Mesos, 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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[StephanEwen]

I think it is better to have the critical cases as dedicated data. The test should include at least one empty array, one short length, one long length (> 256 bytes) and one very long (> 64k). Random arrays can be added, but the important ones should always be in there.

[dianfu]

It makes sense to add dedicated data test. Regarding to 64k length, it fails with OutOfMemoryError 1 times every two runs in my desktop and so I change it to 32k (succeed running the test case 10 times) for test stability.

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CI report:

• 5863668 Azure: SUCCESS Azure: FAILURE

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[dianfu]

@StephanEwen Thanks a lot for the review. Have updated the PR for the test cases.

[dianfu]

@flinkbot run azure

[dianfu]

@StephanEwen @HuangXingBo Thanks a lot for the review. I'm merging this PR to catch up with the bugfix release of 1.13 as this is a series bug for MapState in Python DataStream API. Feel free to let me know if there is anything we could improve.