helpers and recommended way to express the zone identifier

[ffromani]

Currently, the zone ID (NUMA ID) is extracted from the zone (NUMA) name using fragile conventions. Application code uses something along the lines of

func getID(name string) (int, error) {
	var numaID int
	_, err := fmt.Sscanf(name, "node-%d", &numaID)
	if err != nil {
		return -1, fmt.Errorf("invalid zone format zone: %s", name)
	}
	if numaID > maxNUMAId-1 || numaID < 0 {
		return -1, fmt.Errorf("invalid NUMA id range numaID: %d", numaID)
	}
	return numaID, nil
}

Now that we have the helpers package, we should add 1. documentation and recommendations about how to expose zone (or at least NUMA) IDs and a helper function to abstract this part.