Add validation to help users move from usePolicyConfigMap

[hakman]

/cc @justinsb @rifelpet

Fixes #16388

https://kubernetes.io/docs/reference/scheduling/policies/

In Kubernetes versions before v1.23, a scheduling policy can be used to specify the predicates and priorities process. For example, you can set a scheduling policy by running kube-scheduler --policy-config-file or kube-scheduler --policy-configmap .
This scheduling policy is not supported since Kubernetes v1.23. Associated flags policy-config-file, policy-configmap, policy-configmap-namespace and use-legacy-policy-config are also not supported. Instead, use the Scheduler Configuration to achieve similar behavior.

[hakman]

/retest

[justinsb]

Oh ... 1.23!!! Never mind, that's very outside of our support window :-)

/approve
/lgtm

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