Add API testing UI to Aspire dashboard

[captainsafia]

Due to security and maintainability issues, ASP.NET Core templates will not ship with Swagger UI enabled in the future (see dotnet/aspnetcore#54598).

This got me thinking about how valuable it would be to offer an alternative API testing UI that integrated more deeply with Aspire's telemetry and observability options. I would love to have access to an API testing UI in the Aspire dashboard that:

• Allowed me to view and test against endpoints from various services in my application
• Be able to navigate between outgoing requests and the telemetry generated from those requests
• Find requests that generated exceptions and recreate them using the testing UI

While I'm thinking about a UI that is primarily focused on testing for HTTP-based APIs represented with OpenAPI documents, I could see this extending to support testing for other service types (gRPC, etc.)