Proposal: Use generics for underling types

[ythosa]

As i can see, functions such us IndexOf, Min, Max (all from find.go), Some, Contains (all from intersect.go). Has they have the following semantics:

func X[T someConstraint](slice []T, args ...T) 

I think this is an insufficiently effective use of generics because of we can cover underling type too and users who use the library will not have to cast user types.

For example Contains method will be repesented as

func Contains[S ~[]V, V comparable](slice S, v V) bool {
    for _, e := range slice {
        if e == v {
            return true
        }
    }
    return false
}

instead of

func Contains[V comparable](slice []V, v V) bool {
    for _, e := range slice {
        if e == v {
            return true
        }
    }
    return false
} 

According to my estimates, this is not a breaking change, so we can just improve the lives of library users.