fix(parser): replace vulnerable csvjson package with secure internal helper

[ASaiAnudeep]

This PR addresses a security concern regarding the csvjson package, which has a known prototype pollution vulnerability and has been unmaintained for several years.

Changes:

1. New Internal Helper: Created src/helpers/csvjson.js which provides the toObject functionality needed for parsing JMeter CSV results.
2. Security Mitigation: The new helper explicitly filters out __proto__, constructor, and prototype keys from CSV headers to prevent prototype pollution attacks.
3. Dependency Removal: Uninstalled the csvjson package from the project's dependencies.
4. Refactoring: Updated src/parsers/jmeter.js to use the new local helper.
5. Testing: Added tests/csvjson.helper.spec.js to verify the new helper's functionality, including its security features and edge cases (custom delimiters, quotes, etc.).

All existing tests pass, and coverage has been maintained.

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PR created automatically by Jules for task 12796757570366981563 started by @ASaiAnudeep

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