Auto merge of #74532 - fusion-engineering-forks:atomic-from-mut, r=KodrAus
Auto merge of #74532 - fusion-engineering-forks:atomic-from-mut, r=KodrAus

Add Atomic*::from_mut.

The atomic equivalent of [`Cell::from_mut`](https://doc.rust-lang.org/stable/std/cell/struct.Cell.html#method.from_mut).

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