Type class supporting HList union. In case of duplicate types, this operation is a order-preserving multi-set union.
If type T appears n times in this HList and m > n times in M, the resulting HList contains the first n elements
of type T in this HList, followed by the last m - n element of type T in M.
Type class supporting
HListunion. In case of duplicate types, this operation is a order-preserving multi-set union. If typeTappears n times in thisHListand m > n times inM, the resultingHListcontains the first n elements of typeTin thisHList, followed by the last m - n element of typeTinM.