Security features are not listed in GITLAB_FEATURES

Description

We now have an environment variable listing all the EE features available.

GITLAB_FEATURES=audit_events,burndown_charts,contribution_analytics,elastic_search,export_issues,group_webhooks,issuable_default_templates,issue_board_focus_mode,issue_weights,jenkins_integration,ldap_group_sync,merge_request_approvers,merge_request_squash,multiple_ldap_servers,multiple_issue_assignees,multiple_project_issue_boards,push_rules,protected_refs_for_users,related_issues,repository_mirrors,repository_size_limit,scoped_issue_board,admin_audit_log,auditor_user,cross_project_pipelines,db_load_balancing,deploy_board,extended_audit_events,file_locks,geo,ldap_group_sync_filter,multiple_group_issue_boards,object_storage,service_desk,variable_environment_scope,external_authorization_service

This was mainly intended to spot if users have specific features enabled, and run jobs only in that case to avoid wasting of resources.

It actually applies to security features reports in the UI (SAST, DAST, etc), but there is no entry for that.

Proposal

Ensure that security features are listed in the variable. It is fine just to have one single entry for all of them.