WIP: Build image using Debian package

What does this MR do?

• Build a Debian package, to be used instead directly of the Docker image.
• Build the Docker using the aforementioned Debian package

The Docker image is backward compatible with the existing job definitions.

The before-script of the package performs the following tasks if needed:

• install bundler
• install bundler-audit
• clone ruby-advisory-db

These tasks are skipped if the dependencies are already met, making possible to run in an air-gapped environment.

See pipelines using the distro packages in the ruby-bundler test project:

• gitlab-org/security-products/tests/ruby-bundler!65 (closed)

TODO

• Add package dependencies (ruby)
• Add package metadata
• Don't run the analyzer as root

What are the relevant issue numbers?

gitlab-org/gitlab#13477 (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
  • 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