[FLINK-33515][python] Stream python process output to log instead of collecting it in memory

[gaborgsomogyi]

What is the purpose of the change

PythonDriver now collects the python process output in a Stringbuilder instead of streaming it. It can cause OOM when the python process is generating huge amount of output. In this PR I've changed the code not to collect the log but stream it into log line by line.

Brief change log

PythonDriver is collecting the python process output line by line and stream it into log.

Verifying this change

Manually on local machine.

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

[gaborgsomogyi]

cc @gyfora @mbalassi @morhidi

[flinkbot]

CI report:

• ac8e2bd Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

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