Human-readable instance-type node label

[sudomateo]

Context

InstanceMetadata (internal/provider/instances_v2.go) formats the instance type as fmt.Sprintf("%d-%d", ncpus, memoryGiB), producing node.kubernetes.io/instance-type: "4-16" — cryptic in kubectl get nodes -L output.

Scope

Switch to a readable format such as 4vcpu-16gb.

⚠️ This changes the value of an existing node label. Scope includes checking how/whether the label updates on already-initialized nodes (the node controller generally only sets it at initialization) and documenting the behavior for existing clusters.

Done when

New nodes get the readable format and the migration behavior is documented.