Auto merge of rust-lang#141700 - RalfJung:atomic-intrinsics-part2, r=bjorn3

Atomic intrinsics : use const generic ordering, part 2

This completes what got started in rust-lang#141507 by using a const generic for the ordering for all intrinsics. It is based on that PR; only the last commit is new.

Blocked on:
- rust-lang#141507
- rust-lang#141687
- rust-lang/stdarch#1811
- rust-lang#141964

r? `@bjorn3`

Author: bors