[openapi-to-typespec] Missing `@typespec/versioning` import

When converting a swagger to typespec, the `@versioned` decorator is correctly added, but the spec is missing the import and using statements. We need to add the following in the main.tsp ouput:

```
import "@typespec/versioning";

using TypeSpec.Versioning;
```

Showed up when converting the following spec: https://github.com/Azure/azure-rest-api-specs/blob/main/specification/appconfiguration/data-plane/readme.md

cc @joheredi @tadelesh