fix missing GCPBakendPolicy.

[zetxqx]

What type of PR is this?
/kind bug

What this PR does / why we need it:

This is discovered by the Lohi Pipline, where we always use the main helm to install inferencePool and it failed at finding GCPBackendPolicy:

Current inferecePool Helm install will return warning and missing the GCPBackendPolicy for logging. The following as an exmple.

❯ export NAMESPACE=inference-demo
export HELM_RELEASE_NAME=infpool-gemma-2b
❯ helm upgrade -i $HELM_RELEASE_NAME \
  config/charts/inferencepool \
  -n $NAMESPACE \
  --create-namespace \
  --set inferencePool.modelServers.matchLabels.app=vllm-gemma2b \
  --set provider.name=gke \
  --set inferenceExtension.monitoring.gke.enabled=true
Release "infpool-gemma-2b" does not exist. Installing it now.
**I0920 00:19:58.644743 1622628 warnings.go:110] "Warning: unknown field \"spec\""**
NAME: infpool-gemma-2b
LAST DEPLOYED: Sat Sep 20 00:19:56 2025
NAMESPACE: inference-demo
STATUS: deployed
REVISION: 1
TEST SUITE: None
NOTES:
InferencePool infpool-gemma-2b deployed.

W/ the change in this PR, the warning is gone and GCPBackendPolicy is creating again

❯ helm upgrade -i $HELM_RELEASE_NAME \
  config/charts/inferencepool \
  -n $NAMESPACE \
  --create-namespace \
  --set inferencePool.modelServers.matchLabels.app=vllm-gemma2b \
  --set provider.name=gke \
  --set inferenceExtension.monitoring.gke.enabled=true
Release "infpool-gemma-2b" has been upgraded. Happy Helming!
NAME: infpool-gemma-2b
LAST DEPLOYED: Sat Sep 20 00:39:38 2025
NAMESPACE: inference-demo
STATUS: deployed
REVISION: 6
TEST SUITE: None
NOTES:
InferencePool infpool-gemma-2b deployed.
❯ helm status infpool-gemma-2b -n inference-demo --show-resources
NAME: infpool-gemma-2b
LAST DEPLOYED: Sat Sep 20 00:39:38 2025
NAMESPACE: inference-demo
STATUS: deployed
REVISION: 6
RESOURCES:
==> v1/Secret
NAME                                     TYPE                                  DATA   AGE
infpool-gemma-2b-metrics-reader-secret   kubernetes.io/service-account-token   3      19m

==> v1/ConfigMap
NAME                   DATA   AGE
infpool-gemma-2b-epp   1      19m

==> v1/Role
NAME                                          CREATED AT
infpool-gemma-2b-metrics-reader-secret-read   2025-09-20T00:19:58Z
infpool-gemma-2b-epp   2025-09-20T00:19:58Z

==> v1/Service
NAME                   TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)             AGE
infpool-gemma-2b-epp   ClusterIP   34.118.228.139   <none>        9002/TCP,9090/TCP   19m

==> v1/Deployment
NAME                   READY   UP-TO-DATE   AVAILABLE   AGE
infpool-gemma-2b-epp   1/1     1            1           19m

==> v1/Pod(related)
NAME                                    READY   STATUS    RESTARTS   AGE
infpool-gemma-2b-epp-845d58797f-858v8   1/1     Running   0          19m

==> v1/HealthCheckPolicy
NAME               AGE
infpool-gemma-2b   104s

==> v1/ServiceAccount
NAME                                 SECRETS   AGE
infpool-gemma-2b-metrics-reader-sa   0         19m
infpool-gemma-2b-epp   0     19m

==> v1/ClusterRole
NAME                                             CREATED AT
inference-demo-infpool-gemma-2b-metrics-reader   2025-09-20T00:19:58Z
infpool-gemma-2b-inference-demo-epp   2025-09-20T00:19:58Z

==> v1/ClusterRoleBinding
NAME                                                          ROLE                                                         AGE
inference-demo-infpool-gemma-2b-metrics-reader-role-binding   ClusterRole/inference-demo-infpool-gemma-2b-metrics-reader   19m
infpool-gemma-2b-inference-demo-epp   ClusterRole/infpool-gemma-2b-inference-demo-epp   19m

==> v1/RoleBinding
NAME                                                                              ROLE                                               AGE
gmp-system:collector:inference-demo-infpool-gemma-2b-metrics-reader-secret-read   Role/infpool-gemma-2b-metrics-reader-secret-read   19m
infpool-gemma-2b-epp   Role/infpool-gemma-2b-epp   19m

==> v1/GCPBackendPolicy
NAME               AGE
infpool-gemma-2b   104s

==> v1/InferencePool
infpool-gemma-2b   19m

==> v1/PodMonitoring
infpool-gemma-2b   19m


TEST SUITE: None
NOTES:
InferencePool infpool-gemma-2b deployed.

Which issue(s) this PR fixes:

NONE

Does this PR introduce a user-facing change?:

NONE

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[zetxqx]

/assign @ahg-g @kfswain

unfortunately there is a bug. But we are lucky to have lohi pipeline to catch it.

this is also needed in #1616

[zetxqx]

Don't know how the syntax work, but here is a more visualize diff using helm template.

[ahg-g]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ahg-g, zetxqx

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