Add `#[repr(i8)]` to `Ordering`
Add `#[repr(i8)]` to `Ordering`

Followup to #89491 to allow `Ordering` to auto-derive `AsRepr` once
the proposal to add `AsRepr` (#81642) lands.

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