Raise proper exit code when command line arg parsing fails, Add validations for URLs

What does this MR do?

Fixes gitlab-org/gitlab#35000 (closed)

• Raise proper exit code from Python when parsing fails for command-line argument.
• Add validations for args related to URLs (DAST_WEBSITE, DAST_AUTH_URL and DAST_AUTH_EXCLUDE_URLS)
• Add e2e and unit tests for these scenarios.

What are the relevant issue numbers?

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
  • Job definition example
  • Vendored CI Templates (also in CE)
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer