fix: healthchecks for httproute resources which failed to reconcile

[joshdk]

Implements an additional healthcheck for HTTPRoute resources which have a failed status for the "Reconciled" condition type.

Also includes a minor refactor to make it easier to manage the list of condition types to check against.

Checklist:

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[joshdk]

// For some additional context which doesn't necessarily belong in the git history, but will hopefully help anyone searching the same error...

---

We are using the GKE Gateway Controller. Some of the relevant Kubernetes resources are backed by GCP resources, which have their own restrictions and limits.

One specific example is a 64 KB limit on the size of a URL map (see https://docs.cloud.google.com/load-balancing/docs/quotas#:~:text=Size%20of%20URL%20maps). This limit can be hit if enough HTTPRoute resources (with their associated spec/rules) are admitted to the cluster.

When this happens the following error message can be observed in the HTTPRoute status/parents/conditions:

apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute

status:
  parents:
    - conditions:
        - lastTransitionTime: "2026-01-23T18:42:18Z"
          observedGeneration: 1
          reason: ReconciliationFailed
          status: "False"
          type: Reconciled
          message: |
            error cause: gceSync: Update: generic::invalid_argument: Invalid resource usage: ''Size of the url map exceeds the maximum permitted size''.

An example fix for this is to delete a sufficient number of HTTPRoute resources, then wait for the Gateway Controller to re-reconcile after ~5 minutes...

---

ArgoCD currently marks this resource as healthy. This change properly marks these resources as degraded. 💔

Thank you!

[joshdk]

@chansuke @lindeskar (authors who have also touched these files) in case you have opinions.