Add secrets analyzer

What does this MR do?

This adds an analyzer that detects secret leaks in the project.

What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/6719

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary; See https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/9688
• 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
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer

Sid added list of tech used

1. https://github.com/dxa4481/truffleHog
2. https://github.com/techjacker/diffence
3. https://github.com/zricethezav/gitleaks