Boost pods before they are submitted by using a mutating webhook

[norbjd]

Currently, all the boosting logic is inside the controller. The controller listens for pods creations/updates, so pods are boosted after their creation.

In some cases, the boost can't be applied properly (e.g. boosting from 1 CPU to 10 CPU if the initial pod is scheduled on a 4-CPU node won't work). So, we need to boost before the pod is actually submitted to k8s API. Mutating webhook can solve this issue.

When submitting a pod with norbjd.github.io/k8s-pod-cpu-booster-enabled: "true" label, the webhook will now change the CPU requests and limits. Once submitted to the k8s API (with that boost), pod will start normally until it's ready.

After the pod is ready, the controller will still be useful to remove the pod boost. The "unboosting" logic in the controller remains unchanged. But now, the controller will only take care of this "unboosting" logic.

Other notable changes:

• refacto config/ to use kustomize (we need this to inject webhook certificates)
• deploy controller using a Deployment, and not a Daemonset
• temporarily disable e2e test on ubuntu-20.04 because of openssl version incompatibility (-CA parameter is unknown on 1.1.1 version included in ubuntu:22.04). I'll reintroduce that later