Rollup merge of #70281 - xfix:infallible-hash, r=dtolnay
Rollup merge of #70281 - xfix:infallible-hash, r=dtolnay

Implement Hash for Infallible

https://www.reddit.com/r/rust/comments/fmllgx/never_crate_stable_alternative_to/ lists not implementing `Hash` as a reason for the `never` crate. I see no reason not to implement `Hash` for `Infallible`, so might as well do it.

No changes necessary for `!`, because `!` already implements `Hash` (see https://github.com/rust-lang/rust/pull/51404).

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