End to end tests for resource ID with App Hub

We have successfully validated e2e trace propagation for `storage`, `compute`, and `secretmanager`, confirming that the labels generated are correctly enriched with `apphub` attributes.
However, the current approach for integrations tests attempts to **dynamically provision** the App Hub environment (create application -> link service -> wait for service discovery) on every run, which is flaky and crosses over testing App Hub.

Instead, we want to establish a static App Hub resource in a dedicated testing project and should persist across all test runs with a simplified flow:
* perform a client library operation with specific resource names
* wait for a reasonable propagation delay
* verify that the resulting span is correctly enriched with the expected `apphub` attributes

We will use Terraform to manage this one-time setup of the static App Hub environment. This ensures the environment is documented and reproducible if the project is ever deleted.
Reference: [google_apphub_service | Terraform Registry](https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/apphub_service)