chore: move bench package to sites/benchmarks

[janechu]

Pull Request

📖 Description

Moves the private @microsoft/fast-bench package from packages/bench/ to sites/benchmarks/ to better reflect its role as an internal site/tool rather than a publishable package. Also simplifies the root package.json workspaces by using glob patterns (sites/*, examples/*) instead of listing each workspace explicitly.

Changes:

• Move packages/bench/ → sites/benchmarks/ via git mv
• Update root package.json workspaces to use sites/* and examples/* globs
• Update copilot-instructions.md to reflect new location
• Update README.md folder path reference
• Regenerate package-lock.json

📑 Test Plan

• All existing tests pass — the bench package is private with no dependents
• npm run checkchange confirms no change files are needed (private package excluded from beachball scope)
• Workspace resolution verified via npm ls

✅ 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.