Refactor into syslogcef package

[allamiro]

Summary

• replace the ad-hoc scripts with a structured syslogcef package using a src/ layout and pyproject build metadata
• implement robust parsing, CEF encoding, vendor mappings, streaming CLI, and supporting utilities with documentation and changelog updates
• add automated tests, fixtures, CI workflow, pre-commit hooks, and a benchmarking helper for ongoing quality

Testing

• pytest

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