Rollup merge of #76238 - denisvasilik:intra-doc-links-core-iterator, r=jyn514
Rollup merge of #76238 - denisvasilik:intra-doc-links-core-iterator, r=jyn514

Move to intra-doc links for library/core/src/iter/traits/iterator.rs

Helps with #75080.

@jyn514 We're almost finished with this issue. Thanks for mentoring. If you have other topics to work on just let me know, I will be around in Discord.

@rustbot modify labels: T-doc, A-intra-doc-links

Known issues:

* Link from `core` to `std` (#74481):

    [`OsStr`]
    [`String`]
    [`VecDeque<T>`]

graydon/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust