Draft: Adds CI/CD Danger component with its defaults

This enable include all the Danger default rules:

• Changelog
• Change size check
• Commit messages check
• Commits counter check
• MR metadata check
• Reviewer Roulette
• Type labels
• Add labels

All the rules are defined in https://gitlab.com/gitlab-org/ruby/gems/gitlab-dangerfiles/-/tree/master/lib/danger/rules?ref_type=heads

The existing Dangerfile was refactored into a separate directory to keep the code clean, but it should still be active.

The rules for when to trigger the Danger job were maintained, as well as the decided stage name.

The job name was changed from danger_checks to danger-review for consistency.