add kernel version check for kubeadm upgrade

[pacoxu]

Currently, only root check and corefile migration check before upgrading node.

// RunRootCheckOnly initializes checks slice of structs and call RunChecks
func RunRootCheckOnly(ignorePreflightErrors sets.Set[string]) error {
	checks := []Checker{
		IsPrivilegedUserCheck{},
	}

	return RunChecks(checks, os.Stderr, ignorePreflightErrors)
}

xref kubernetes/kubernetes#102612 (comment)

• For new clusters: In system-validator, kernel version should be 4.19+; recommend version 5.8 for cgroup v2 system-validators#37 was merged recently.
• For upgrades, I think there is no kernel version check there. I need to verify to see if we need to add a warning for upgrading.

[neolit123]

+1

in upgrade apply and upgrade node preflight we run RunRootCheckOnly, which should be changed to maybe a new RunUpgradeCheks func with what is needed.

then if RunRootCheckOnly is no longer used anywhere it can be removed.

[pacoxu]

I did a quick check for all preflight checks.

• Currently, we may only add to SystemVerificationCheck to RunUpgradeCheks.

[pacoxu]

BTW, should this update be done after bumping https://github.com/kubernetes/system-validators/ or not a problem?

[neolit123]

running the kernel checks on upgrade can be done regardless.

also, i think bumping system validators should be done only after is done:

• Update the kernel configuration for cgroup v2 system-validators#36