Correlate CPU/Memory usage with load tests

[flavio]

We would like run the load tests against the Kubewarden stack and be able to track the CPU and memory consumption of Policy Server (and different portions of our stack) while the tests are run.

k6 seems to be a good solution for that.

This branch contains some code that can be used to perform load tests using k6.

Acceptance criteria

• Existing tests are rewritten to be run with k6 #28
• It's not clear how the load tests can be run #29

Future work

• Run the load tests inside of a Kubernetes cluster, targeting a Kubewarden stack deployed with our helm charts
• Collect CPU and memory usage patterns of the Kubewarden stack while the tests are run