[FLINK-39572][python] Do not log the Beam environment payload

[MartijnVisser]

What is the purpose of the change

flink-python's copy of Beam's DefaultJobBundleFactory logged the whole RunnerApi.Environment, whose process payload holds every environment variable of the Python worker, i.e. of the TaskManager. See FLINK-39572.

Brief change log

• The three log statements print the environment's urn.
• Only the variables the environment manager sets are passed to the worker explicitly; it inherits the rest through Beam's ProcessBuilder, as before.

Verifying this change

This change added tests and can be verified as follows:

• DefaultJobBundleFactoryTest runs the real close path with a marker variable in the payload; red without the first commit.
• ProcessPythonEnvironmentManagerTest#testProcessEnvironmentOnlyContainsManagedVariables; red without the second.
• test_dependency.py::test_set_environment now reads a variable set before the gateway JVM starts, so inheritance is covered.

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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[flinkbot]

CI report:

• 73ad8b4 Azure: SUCCESS

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[dianfu]

@MartijnVisser Thanks for the PR. LGTM.