Implement and wire up a validation helper to validate policy fields before attempting to save the policy

[david-martin]

Ideally part of this helper https://github.com/Kuadrant/console-plugin/blob/main/src/utils/createResource.tsx

If server side validation is relied on, the promise rejection from https://github.com/openshift/console/blob/master/frontend/packages/console-dynamic-plugin-sdk/docs/api.md#k8screateresource may be useable to do this.