[http-client-csharp] spector case http/client/naming cannot compile

[ArcturusZhang]

This spector has a sub-client ClientModel and a model ClientModel under the same namespace: https://github.com/Azure/typespec-azure/blob/20444c9531da7b8b1bba8932d29269e96cacb270/packages/azure-http-specs/specs/client/naming/main.tsp#L147-L164

In our generated code, now we just generated a client type ClientModel, and a model type ClientModel.
This will never compile because they both have a parameterless constructor. And on the other hand, even if this could compile, this will never work.

This issue will not happen on main branch. The code on main branch also have one client ClientModel and one model ClientModel but they are defined in different namespaces therefore it is actually fine.
But with the "honor tsp namespace" feature, they are now defined in the same namespace, and we now have a trouble.

[ArcturusZhang]

TypeSpec itself allows us to define a model with the same name under a namespace, such as:

namespace Foo {
    model Foo {}
}

We have checks on those clientName decorators to ensure within the same namespace, we do not have models with the same name.
But we did not check model-client cases because typespec itself allows it. @live1206

Should we do a check in the emitter and report another diagnostic on this, and then automatically rename the model? Or we should ignore it and fix on its spec?