[Docs] Use AuthPolicy instead of AuthConfig for most of the guides

[pehala]

Currently, we lack proper guides for AuthPolicy, while we use AuthPolicy in RLP docs (e.g. https://docs.kuadrant.io/kuadrant-operator/doc/user-guides/authenticated-rl-with-jwt-and-k8s-authnz/), in the Authorino section we use AuthConfigs, which make sense for an Authorino-only documentation but not for a Kuadrant one.