This patch updates VPInterleaveRecipe::print to print the actual defined
VPValues for load groups and the store VPValue operands for store
groups.
The IR references may become outdated while transforming the VPlan and
the defined and stored VPValues always are up-to-date.
Would have been nice to iterate over the recipe's operands and/or def VPValues, instead of calling getOperand()/getVPValue() for each, but the former does not tell where the gaps are.