Summary: Add predefined metric for Open Critical Severity Vulnerabilities count

Description: Provide a predefined metric that tracks the current "point-in-time" count of Open Critical Severity Vulnerabilities. While remediation time is useful, a volume-based metric is essential for dashboarding and component health scorecards.

Customer Goal: Use the count of open critical vulnerabilities as a direct input for Component Health scores to prevent high-risk components from appearing "Healthy."