Rollup merge of #34688 - GuillaumeGomez:double_ended_iterator, r=steveklabnik
Rollup merge of #34688 - GuillaumeGomez:double_ended_iterator, r=steveklabnik

Improve DoubleEndedIterator examples

Fixes #34065.

r? @steveklabnik

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