Change orderings of Debug for the Atomic types to Relaxed.

[Noratrieb]

This reduces synchronization between threads when debugging the atomic types. Reducing the synchronization means that executions with and without the debug calls will be more consistent, making it easier to debug.

We discussed this on the Rust Community Discord with @ibraheemdev before.

[rust-highfive]

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[rust-highfive]

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[scottmcm]

LLVM docs for Relaxed, for anyone else looking at this: https://www.llvm.org/docs/Atomics.html#monotonic

This seems reasonable to me. Relaxed provides no ordering compared to other things, but anyone using formatting-plus-parsing and assuming it's causing a particular ordering definitely seems like they're doing it wrong, so that's fine.

@bors r+

[bors]

📌 Commit d11667f has been approved by scottmcm