chore(fast-html): use @microsoft/fast-build to build performance-metrics fixture

[janechu]

Pull Request

📖 Description

Adds the performance-metrics test fixture to @microsoft/fast-html and generates its index.html using @microsoft/fast-build, consistent with the other fixtures.

The performance-metrics fixture covers deferred hydration with configurable delays (defer-delay). It renders 14 fast-card elements across three delay groups (0ms, 150ms, 300ms) and verifies that @microsoft/fast-build correctly pre-renders their shadow DOM content.

Redundant {{binding}} attrs (willHydrate, didHydrate, hydrationDuration) have been removed from entry elements — their property names match the root state.json keys so they are passed implicitly. Static attrs (needs-hydration, defer-hydration, defer-delay, displayDelay) are preserved. The duplicate changefile from the original two commits has also been removed.

🎫 Issues

No open issues directly addressed.

📑 Test Plan

• npm run build:fixtures in packages/fast-html runs cleanly and regenerates performance-metrics/index.html with all 14 fast-card elements correctly rendered from root state.
• All other fixture outputs are unchanged.

✅ Checklist

General

• I have included a change request file using $ npm run change
• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation and followed the standards for this project.