We want to introduce feature gates in k0s, in particular, we need one for single stack IPv6.

We can take "inspiration" from kubernetes and do something very similar. Kubernetes has a flag `--featuregates=...,Feature[=(true|false)].

Implementing this feature would require:
1- Documentation for current feature gates
2- Documentation for removed feature gates
3- A new flag for this
4- Actual implementation. Should we use k8s.io/component-base/featuregate ? It's consistent with kubernetes, we already import k8s.io/component-base so it wouldn't be adding new dependencies but it seems a bit overcomplicated for what we need. Nonetheless it's probably the most sane option.