[Feature request] http-server-csharp: Expand output-type to support multiple choice: controllers, models, etc.

### Clear and concise description of the problem

Earlier, the ProviderHub package supported multi-choice configuration key:

```json
"code-kind": "controller | model | default: both"
```

Can the new HttpServer package support something similar to that via the already configuration key `output-type`?

Specifically, what I want to generate:

- models
- controllers

What I don't want:

- docs/*.md
- Program.cs
- README.md

### Checklist

- [x] Follow our [Code of Conduct](https://github.com/microsoft/typespec/blob/main/CODE_OF_CONDUCT.md)
- [x] Read the [docs](https://typespec.io/docs/).
- [x] Check that there isn't already an issue that request the same feature to avoid creating a duplicate.