Connect to gemnasium-db repo

What does this MR do?

Make the analyzer leverage the gemnasium-db repo directly instead of connecting to the Gemnasium API.

What are the relevant issue numbers?

gitlab-org/gitlab#14630 (closed)

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
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer