Review and document AI-related specs that block deployments

• Review E2E AI specs that block staging deploys
• Add blocking test for Duo Chat
• Document E2E AI specs that block staging deploys in coverage issue
• Document E2E AI specs that run in MRs in coverage issue
• Document E2E AI specs that block MRs in coverage issue
• Add code suggestions API spec back to :smoke to block deployments if broken gitlab-org/gitlab!162952 (merged)
• :block when webide code suggestions fails