Requests from "always allowed" namespace should not be sent to Wasm evaluators

[flavio]

Policy Server administrator can configure a special namespace that is not affected by the policies, meaning all the operations inside of it are always allowed. This is commonly used to exclude Kubewarden's namespace, preventing user's policies from damaging the whole stack (and hence causing an outage to the whole cluster).

Currently, the requests assigned to this namespace are still processed by the WebAssembly evaluators, but later the evaluation results are simply discarded and the request is accepted. As a minor optimization, we should change our code to immediately accept a request involving the "special namespace", without having to waste CPU cycles doing WebAssembly evaluations.