Conditionalize PUP sizing on load balancers' needs
Currently an element's PUP sizer is called before the LB strategy runs so that that information can possibly be taken into account by the strategy. However, the information is not used by most all strategies and when debugging application PUP code it has caused slight confusion for users. In addition, the PUP sizer is called twice if you are using MetaLB. So a LB strategy should be able to say if it wants the PUP size or not.