Samples directory warning should appear only when needed

[folmos-at-orange]

Description

Currently, when the samples directory is not available the following warning appears systematically:

/builds/ai4ops/ai4ops-core/.venv/lib/python3.14/site-packages/khiops/core/internals/runner.py:1043: UserWarning: Sample datasets location does not exist (/root/khiops_data/samples). Execute the kh-download-datasets script or the khiops.tools.download_datasets function to download them.
    self._initialize_default_samples_dir()

This pollutes the logs in CI and production systems using the library, where most likely the samples directory is not necessary.

Questions/Ideas

• I think this warning should be triggered only when:
  • get_samples_dir is called
    • In this case it should be an exception
  • print_status is called

[popescu-v]

Should be addressed in #456.