Update Python 3.8 Detection Logic to Use Detected Version

[kbukum1]

What are you trying to accomplish?

This PR updates the detection logic for Python 3.8 to ensure that detected_version is consistently used across the deprecation and unsupported checks.

This change addresses scenarios where raw_version is either nil or diverges from detected_version, improving the reliability of version checks and the accuracy of deprecation and unsupported notices for Python.

Why?

• To align the detection and handling of Python versions with detected_version as the authoritative source.
• To resolve inconsistencies and potential errors when raw_version is nil or different from detected_version.
• To ensure a consistent and reliable experience for Dependabot users managing Python dependencies.

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Anything you want to highlight for special attention from reviewers?

• The unsupported? and related methods have been updated to prioritize detected_version, falling back to raw_version only when necessary.
• Test cases have been added to validate scenarios such as:
  • Proper detection of Python 3.8 as deprecated or unsupported.
  • Handling cases where raw_version is nil or mismatched with detected_version.
  • Correct functioning of edge cases related to Python 3.8 detection and warnings.

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How will you know you've accomplished your goal?

• All tests in the suite, including those for Python version detection and handling, pass successfully.
• Python 3.8 deprecation and unsupported checks work consistently, using detected_version in all scenarios.
• Edge cases involving raw_version discrepancies or absence are correctly handled without errors or inconsistencies.

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Checklist

• I have run the complete test suite to ensure all tests and linters pass.
• I have thoroughly tested the changes to confirm they work as intended, including additional tests for the new detection logic.
• I have provided clear and descriptive commit messages for the changes.
• I have included a detailed description of the issue addressed, the solution implemented, and the rationale for the changes.
• I have ensured the code is well-documented, with clear explanations for any updated or added logic.

[kbukum1]

Review Tip: For metrics we want to use the python version from ecosystem that dependabot runs on instead of parsed version.

[kbukum1]

Review Tip:

• Detected Version: Parsed from manifest or lock files to identify the project's specified language version.
• Raw Version: Retrieved via pyenv exec python --version to determine the runtime Python version.

This distinction ensures accurate deprecation checks and metrics collection.