Replace deprecated distutils and pkg_resources with modern alternatives

[dhruvildarji]

Summary

• Replace distutils.version.LooseVersion fallback with direct packaging.version.Version import (distutils was removed in Python 3.12)
• Replace pkg_resources fallback with direct importlib.metadata.metadata import (available since Python 3.8, which is already the minimum required by numpy 1.24.4)
• Add packaging as an explicit dependency in requirements.txt

Motivation

The distutils module was deprecated in Python 3.10 and removed entirely in Python 3.12 (PEP 632). Similarly, pkg_resources from setuptools is deprecated in favor of importlib.metadata (available since Python 3.8).

Since the project already requires Python 3.8+ (numpy 1.24.4 requires it), both packaging.version.Version and importlib.metadata are guaranteed to be available, making the try/except fallbacks unnecessary.

This partially addresses #1128 by removing deprecated imports that cause warnings and failures on newer Python versions.

Changes

• scenario_runner.py: Replaced try/except import blocks with direct imports
• requirements.txt: Added packaging as an explicit dependency (was previously only used if available)

Test plan

• Verify python scenario_runner.py --help runs without import errors on Python 3.8+
• Verify pip install -r requirements.txt succeeds and includes packaging

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