rollup merge of #20215: csouth3/hashmap-rename

Rename struct `Entries` to `Iter` in hash/table.rs and hash/map.rs, to match the naming convention of rust-lang/rfcs#344.

This is a [breaking-change].

diff --cc src/libstd/collections/hash/map.rs
Simple merge

diff --cc src/libstd/collections/hash/table.rs
Simple merge