[SDKAgent] Prevent SDK generation before namespace review pass for first onboard service

We got a weird [PR](https://github.com/Azure/azure-sdk-for-go/pull/27046) for a release request. The service has not passed the namespace review since it is a first onboard service. And it used some placeholder for the package name in the `tspconfig.yaml`, which created the weird PR. I think we should not allow the trigger SDK generation before the namespace review pass for first onboard service. Also, it's better to ensure the `tspconfig.yaml` changed corrected according to the namespace review result before doing the SDK release.

Start by tracing the SDK generation trigger for release requests and how first-onboard namespace review status is represented. Inspect the linked PR and the service's tspconfig.yaml to understand the placeholder package name. Done means generation is blocked until namespace review passes and the configuration reflects its result.

Written by the indexing model from the issue text.