Document and validate steps for Upgrading an OpenShift Container Platform cluster configured for manual mode with GCP Workload Identity.

Update the "Using manual mode with GCP Workload Identity" documentation to include steps for upgrading the cluster and include detailed examples regarding how to update existing credentials with new permissions that have changed in the release image for the target upgrade version.

We should ensure that an updated permission is added to an existing credential as part of the validating the steps.

AWS STS documentation which can serve as a starting point for the steps for GCP Workload Identity: https://docs.openshift.com/container-platform/4.11/authentication/managing_cloud_provider_credentials/cco-mode-sts.html#sts-mode-upgrading