AKS RP should mark edge node as drifted if configuration mismatch

[wenxuan0923]

RP (source of truth) marks intent / mismatch: When MC is upgraded (control-plane + desired node version) and an edge node is still on an older expected version/config, having RP stamp something like:

aks.microsoft.com/drifted=true

(maybe) plus a reason and desired version annotation

Later we should have the agent (aks-flex-node) on the edge node watching for that signal and perform the reconciliation action (not in preview scope)