Handle overflow errors in date conversion recipes

[RamiNoodle733]

Summary

• treat OverflowError from dateutil.parser.parse() as a parse failure for the existing errors= modes
• preserve current behavior when errors is unset by re-raising the exception
• add focused regression coverage for both parsedate() and parsedatetime()

Fixes #857

Testing

• PYTHONPATH=. python -m pytest tests/test_recipe_overflow.py -q using the exact changed recipe code and regression test: 6 passed
• python -m compileall -q sqlite_utils tests/test_recipe_overflow.py
• Black and flake8 were not installed in the execution environment, so those checks were not run locally

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📚 Documentation preview 📚: https://sqlite-utils--858.org.readthedocs.build/en/858/