feat: Export vulnerability length constants

What does this MR do?

Export length constants to make referencing these easier for analyzers, such as in cases where we need to trim the fields, for example security-code-scan!150 (merged)

We should really do this generically so we don't have to manually trim per analyzer but there's no good abstraction currently since we rely on a relatively independent ConvertFunc to handle all conversion logic. We could do so within command.Run() but either way we should export these first. report seems like a sufficiently authoritative package to contain the constants and a future TODO to add mirror all schema maxLengths here as well.

What are the relevant issue numbers?

N/A

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Job definition updated, if necessary
  • Auto-DevOps template
  • Job definition example
  • CI Templates
• Ensure the report version matches the equivalent schema version
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer