add new cases for decorator @convenientAPI & @protocolAPI applied at the namespace + interface level

The protocolAPI decorator docs are [here](https://azure.github.io/typespec-azure/docs/libraries/typespec-client-generator-core/reference/decorators/#@Azure.ClientGenerator.Core.protocolAPI) and the convenientAPI decorator docs are [here](https://azure.github.io/typespec-azure/docs/libraries/typespec-client-generator-core/reference/decorators/#@Azure.ClientGenerator.Core.convenientAPI).

Goal:
Add test case in folder https://github.com/Azure/typespec-azure/tree/main/packages/azure-http-specs/specs/azure/client-generator-core

Ask:

Add cases:
- applying each decorator at the namespace level
- applying each decorate at the interface level