Standardize Package Details Fetching and Integrate Python Details Fetcher

[kbukum1]

What are you trying to accomplish?

This PR introduces a generic package details finder to standardize the way Dependabot fetches package metadata across different ecosystems. It integrates the Python package details fetcher into this generalized structure to improve maintainability and extensibility.

• Implements a generic package details finder to unify package metadata retrieval.
• Updates the Python package details fetcher to use this new structure.
• Uses Python JSON API ({url}/pypi) to fetch metadata, including release dates, when available.
• Falls back to HTML-based details fetching if the JSON API is unavailable or fails.

Anything you want to highlight for special attention from reviewers?

• Ensures that the JSON API is prioritized while keeping the HTML fallback mechanism functional.
• Validates that the existing Python package registry handling logic remains intact after refactoring.
• Reviewers should confirm that the metadata retrieval logic remains consistent across different registry URLs, including private registries.

How will you know you've accomplished your goal?

• The new generic package details finder correctly integrates with the Python ecosystem.
• The system retrieves package metadata, including release dates, using the JSON API when possible.
• If the JSON API is unavailable, the HTML fallback mechanism still provides accurate metadata.
• All tests pass, and additional test cases confirm that both JSON-based and HTML-based metadata fetching work correctly.

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Checklist ✅

• I have run the complete test suite to ensure all tests and linters pass.
• I have thoroughly tested my code changes to ensure they work as expected, including adding additional tests for new functionality.
• I have written clear and descriptive commit messages.
• I have provided a detailed description of the changes in the pull request, including the problem it addresses, how it fixes the problem, and any relevant details about the implementation.
• I have ensured that the code is well-documented and easy to understand.