[sample gen] Missing recursive processing of base class properties caused inherited properties to lose mapping

[v-jiaodi]

spec repo case: https://github.com/Azure/azure-rest-api-specs/tree/main/specification/applicationinsights/ApplicationInsights.LiveMetrics
typespec:

model DocumentBase {
  documentType: string;
  Properties?: string[];
}

model ExceptionDocument extends DocumentBase {
  ExceptionType: string;
  ExceptionMessage: string;
}

model RequestModel{
    Documents:ExceptionDocument[];
}
@route("/documents")
interface Documents {
  @post
  publish(@body body: RequestModel): void;
}

## Example

```json
{
  "title": "Publish Documents",
  "operationId": "Documents_publish",
  "parameters": {
    "body": {
      "Documents": [
        {
          "documentType": "Exception",
          "ExceptionType": "System.ArgumentNullException",
          "ExceptionMessage": "Value cannot be null",
          "Properties": ["stream-1", "stream-2"]
        }
      ]
    }
  }
}

Samples

async function publishDocuments(): Promise<void> {
  const endpoint = process.env.TESTING_ENDPOINT || "";
  const client = new TestingClient(endpoint);
  await client.publish({
    documents: [
      {
        documentType: "Exception",
        exceptionType: "System.ArgumentNullException",
        exceptionMessage: "Value cannot be null",
        Properties: ["stream-1", "stream-2"], // ❌ Properties should be properties
      },
    ],
  });
}
async function main(): Promise<void> {
  await publishDocuments();
}
main().catch(console.error);

root case: https://github.com/Azure/autorest.typescript/blob/main/packages/typespec-ts/src/modular/helpers/typeHelpers.ts#L96
buildPropertyNameMapper does not process the base class properties.