Docs: Add documentation for Security labels

• Start this issue's title with Docs: or Docs feedback:.

Problem to solve

&18010#problem-to-solve

Further details

Proposal

• add a page called "Security attributes", something like https://docs.gitlab.com/user/application_security/security_attributes/
• clarify in the Security configuration section that not all Security configuration features are available at all tiers - this new Security attributes feature is GitLab Ultimate
• add a note about the feature flag
• add a description of the feature
• add screenshots of the feature

Who can address the issue

Other links/references