docs: Add benchmarking documentation and V2 API guide

[jioffe502]

• Add new Benchmarking section with testing framework guide
• Add MIG benchmarking guide for Kubernetes/Helm deployments
• Add V2 API Guide to Developer Guide section
• Update README with benchmarking quick start and links
• Update mkdocs navigation structure

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.
• If adjusting docker-compose.yaml environment variables have you ensured those are mimicked in the Helm values.yaml file.