copilot coding agent extension: enhanced role assignment templates for common scenarios

[potential enhancement]

## Summary
Provide pre-configured role assignment templates for common development scenarios to simplify setup and improve security best practices.

## Description
Instead of manually specifying roles, users should be able to select from common scenario templates:
- Web application development (App Service, Key Vault, Storage)
- Data analytics (Synapse, Data Factory, Storage)
- Container applications (AKS, Container Registry, Key Vault)
- Serverless applications (Functions, Event Grid, Cosmos DB)