Rollup merge of #34988 - frewsxcv:vec-windows, r=GuillaumeGomez
Rollup merge of #34988 - frewsxcv:vec-windows, r=GuillaumeGomez

Doc example improvements for `slice::windows`.

* Modify existing example to not rely on printing to see results
* Add an example demonstrating when slice is shorter than `size`

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