IntersectBy,DifferenceBy,UnionBy for slice

[btagrass]

for example: DifferenceBy[T any](list1, list2 []T, equal func(t1, t2 T) bool) ([]T, []T)

[takanuva15]

Can we make it accept a variadic number of collections?

[lydamian]

+1 this it would be super helpful