[FLINK-27074] Change python_job.py to write to unique paths within TEST_DATA_DIR

[twthorn]

What is the purpose of the change

Change python_job.py to use the shared TEST_DATA_DIR environment variable & directory for writing test output data (rather than its current custom logic for creating/removing an output directory). Also, generates a unique directory name within TEST_DATA_DIR so e2e tests that use this file multiple times do not run into name conflicts.

Brief change log

• Change python_job.py to write to unique paths within TEST_DATA_DIR

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

[flinkbot]

CI report:

• 9df66fdad3309e0e5ad33ffe656a07760e1eaa68 Azure: FAILURE

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot run azure re-run the last Azure build

[twthorn]

@MartijnVisser Can you review this when you get the chance or know someone who could? Issue is a bit old but still open, and the file hasn't been changed since before this PR was created, so it's still up to date.

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[github-actions[bot]]

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