Rollup merge of #72141 - kornelski:dontsleep, r=joshtriplett
Rollup merge of #72141 - kornelski:dontsleep, r=joshtriplett

Warn against thread::sleep in async fn

I've seen `thread::sleep` wrecking havoc in async servers. There's already an [issue for clippy](https://github.com/rust-lang/rust-clippy/issues/4377), but the std docs could warn against it too.

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