feat: Added Exit codes and updated unit tests #547

[LaKeishaTurnerSlalom]

secureli-375 https://github.com/slalombuild/secureli/issues/375

Added Additional Exit Codes based on error types as discussed. Passing exitCode to the ScanFailure class

Changes

• Added Exit Codes
• Updated ScanFailure
• Updated Unit Tests
• Verified no additional errors

Testing

Clean Code Checklist

• [x] Meets acceptance criteria for issue
• [x] New logic is covered with automated tests
• [ ] Appropriate exception handling added
• [ ] Thoughtful logging included
• [ ] Documentation is updated
• [ ] Follow-up work is documented in TODOs
• [ ] TODOs have a ticket associated with them
• [x] No commented-out code included