[TypeSpec APIView] Services with multiple versioning enums

APIView crashes on this PR:
https://github.com/Azure/azure-rest-api-specs/pull/31747

This happens because the service is not marked with `@versioned`. Instead the decorator appears on a child namespace.

Start by reproducing the APIView crash with Azure REST API Specs PR #31747, then trace how services and child namespaces are handled when multiple versioning enums are present. Done means APIView no longer crashes when the service lacks @versioned but a child namespace has the decorator.

Written by the indexing model from the issue text.