refactor(examples): replace os.system with native python libs in create_dataset.py

[lucasbazan]

Description

Refactored examples/orderbook_data/create_dataset.py to replace os.system calls (which invoked Linux-specific shell commands like cp, tar, and chmod) with native Python libraries (shutil, tarfile, os).

Key changes:

1. Replaced cp with shutil.copy.
2. Replaced tar shell command with the tarfile module.
3. Replaced chmod 777 with os.chmod using safer permissions (0o755), ensuring the script doesn't grant excessive world-writable permissions.
4. Introduced a lambda helper and a loop to handle the "SH" and "SZ" subfolders, removing code duplication.

Motivation and Context

1. Cross-Platform Compatibility: The previous implementation relied on Linux shell commands (cp, tar, chmod) via os.system, causing the script to fail on Windows environments. Native Python libraries ensure the script runs correctly on Windows, Linux, and macOS.
2. Security: Using os.system with shell commands can lead to command injection risks if variables are not sanitized. Additionally, chmod 777 is a security risk. The new implementation follows the principle of least privilege.
3. Code Quality: The refactoring removes redundant code blocks by iterating over the target subfolders.

How Has This Been Tested?

• Pass the test by running: pytest qlib/tests/test_all_pipeline.py under upper directory of qlib.
• If you are adding a new feature, test on your own test scripts.

Test Description:
I manually ran the create_dataset.py script locally to verify that:

1. The .tar.gz files are correctly copied to the destination.
2. The archives are correctly extracted into the SH and SZ folders.
3. No shell errors are raised.

Types of changes

• Fix bugs (fixes script failure on non-Linux OS)
• Add new feature
• Update documentation

NOTE: I know that this is a demo script, but is good to demonstrate with a secure code.

[lucasbazan]

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