Use kubeconfig file to auth to GKE instead of oauth2 token

[hussein-awala]

closes: #31648

Before the PR #29266, we used to create a temporary configuration file by running the command gcloud container clusters get-credentials. We would then use this file in the Kubernetes client. The get-credentials command configures kubectl to automatically refresh its credentials using the same identity as gcloud.

However, the #29266 introduced a new pod GKE hook that uses the following client code:

ApiClient(
    configuration,
    header_name="Authorization",
    header_value=f"Bearer {access_token}",
)

This client uses static oauth2 credentials and cannot refresh them when they expire. Since the default lifetime for GCP credentials is 3600 seconds, the operator fails with an Unauthorized exception after one hour.

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