test(parsers): Add tests for js and Python parsers

[JigyasuRajput]

Description:

Fixes - #4874

This PR improves test coverage for Javascript and Python parsers

Changes:

• JavaScript Parser:
  • Added tests for process_yarn_lock (yarn.lock regex parsing).
  • Added tests for process_package_lock_lockfile_v2 (package-lock.json v2 parsing).
• Python Parser:
  • Tested run_checker in PythonRequirementsParser for subprocess errors.
  • Tested run_checker in PythonParser for invalid METADATA/PKG-INFO handling.

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Testing:

• All tests pass successfully via pytest.
• Ensures key parsing logic is correctly validated.