test: add context-aware integration tests

[fabriziosestito]

Description

This PR introduces context-aware integration tests.
The following runtimes have been tested by using context-aware test policies:

• wapc: https://github.com/fabriziosestito/context-aware-test-policy
• opa: https://github.com/fabriziosestito/context-aware-test-opa-policy
• gatekeeper: https://github.com/fabriziosestito/context-aware-test-gatekeeper-policy

Todo

• [ ]: move the test policies to the Kubewarden organization

To be able to run the tests, a mock Kubernetes client was created by using this guide: https://kube.rs/controllers/testing/#unit-tests-with-mocks
Since there is nothing equivalent to envtest in Rust, using a mock allows us to save some CI time (and effort) by relying on a mock kube-rs Client.

An alternative could have been setting up a real cluster, but dealing with the isolation and testcontainers was a big downside and the return on investment wasn't worth it for this type of test, since the goal is testing the policy evaluator and considering we already have e2e tests in place.

[jvanz]

LGTM. I just have a quick question. I'll not give a "approved" flag because the PR is a draft and I know that Fabrizio is working on this still.

[flavio]

Love it! One minor nitpick, see my comment.

I would start the transfer process of the test policies to the kubewaden organization, and then change this PR to consume the images from there. Then we can merge it

[viccuad]

LGTM!