Rollup merge of #51701 - anirudhb:master, r=frewsxcv
Rollup merge of #51701 - anirudhb:master, r=frewsxcv

Better docs for copy_from_slice & clone_from_slice

I copy-pasted the text from clone_from_slice to copy_from_slice :smile:

@steveklabnik feel free to suggest changes.

edit: closes #49769

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