[algorithm] new way to implement Fibonacci using closure for any iterator and any sequence.

.swift

let res4 = Array(
    AnySequence { () -> AnyIterator<Int> in
        var t1 = (0, 1)
        return AnyIterator<Int> {
            let (a, b) = t1
            t1 = (b, a + b)
            return b
        }
    }
    .prefix(10)
)

res4

// [1, 1, 2, 3, 5, 8, 13, 21, 34, 55]