estd: Add mechanism to expand a variadic set of expresions
estd: Add mechanism to expand a variadic set of expresions

This is useful when checking concepts for a variadic argument pack.

iankronquist/atria,respu/atria,iankronquist/atria,dodheim/atria,respu/atria,lyrl/atria,bowlofstew/atria,bowlofstew/atria,AbletonAG/atria,manashmndl/atria,respu/atria,lyrl/atria,Ableton/atria,kod3r/atria,iankronquist/atria,Ableton/atria,shaunstanislaus/atria,AbletonAG/atria,AbletonAG/atria,shaunstanislaus/atria,bowlofstew/atria,lyrl/atria,kod3r/atria,manashmndl/atria,kod3r/atria,Ableton/atria,dodheim/atria,shaunstanislaus/atria,dodheim/atria,manashmndl/atria