Document version skew policy #6305
Description
Different kube components have different supported version skews. It seems the control plane components mostly only allow one minor version difference (1.22.x => 1.23.x) both for running and when upgrading. Major upgrades are not supported at all (but there isn't a v2 anyway), but other upgrades should be done 1 minor at a time and preferably from latest patch to latest patch.
Kubelet seems to allow it to be 3 minor versions behind (1.22.x should still work with a 1.25.x control plane) when running but doesn't seem to directly mention if it's ok to upgrade in steps of 3 minors. Kubelet can never be newer than kube-api.
I think k0s wants to just follow these and not offer any "extended version skew support". Perhaps even only officially support 1 minor for everything.
It's only shortly mentioned in autopilot docs.
Related: k0sproject/k0sctl#923