Add more functionality to where clause

The where clause is compile-time check, it's a great idea. but I think we can make it even more great by add some more functionality to it.

1. range check: require port is constexpr implicitly

fn foo(port: usize)
    where   port <= 65535,
            port > 1000,
            port in 1000..65536 // or this one, much better
{}

2. make it general purpose

let foo = 1..500 where _ % 4 == 0 // something like this ( _ maybe better with it )
let foo = 1..100 where it % 2 == 0 //ah much better

Motivation
In 1, it will improving some performent and much easier to optimize code, not letting code jump around
In 2, just let where everywhere, I think people will love it

Start with issue #2715 and review its existing discussion, focusing on the proposed range checks and general-purpose where expressions. Determine whether the scope and syntax can be narrowed into a concrete RFC; done requires an agreed design and clear acceptance through the RFC process.