Rollup merge of #97423 - m-ou-se:memory-ordering-intrinsics, r=tmiasko

Simplify memory ordering intrinsics

This changes the names of the atomic intrinsics to always fully include their memory ordering arguments.

```diff
- atomic_cxchg
+ atomic_cxchg_seqcst_seqcst

- atomic_cxchg_acqrel
+ atomic_cxchg_acqrel_release

- atomic_cxchg_acqrel_failrelaxed
+ atomic_cxchg_acqrel_relaxed

// And so on.
```

- `seqcst` is no longer implied
- The failure ordering on chxchg is no longer implied in some cases, but now always explicitly part of the name.
- `release` is no longer shortened to just `rel`. That was especially confusing, since `relaxed` also starts with `rel`.
- `acquire` is no longer shortened to just `acq`, such that the names now all match the `std::sync::atomic::Ordering` variants exactly.
- This now allows for more combinations on the compare exchange operations, such as `atomic_cxchg_acquire_release`, which is necessary for #68464.
- This PR only exposes the new possibilities through unstable intrinsics, but not yet through the stable API. That's for [a separate PR](https://github.com/rust-lang/rust/pull/98383) that requires an FCP.

Suffixes for operations with a single memory order:

| Order   | Before       | After      |
|---------|--------------|------------|
| Relaxed | `_relaxed`   | `_relaxed` |
| Acquire | `_acq`       | `_acquire` |
| Release | `_rel`       | `_release` |
| AcqRel  | `_acqrel`    | `_acqrel`  |
| SeqCst  | (none)       | `_seqcst`  |

Suffixes for compare-and-exchange operations with two memory orderings:

| Success | Failure | Before                   | After              |
|---------|---------|--------------------------|--------------------|
| Relaxed | Relaxed | `_relaxed`               | `_relaxed_relaxed` |
| Relaxed | Acquire | :x:                      | `_relaxed_acquire` |
| Relaxed | SeqCst  | :x:                      | `_relaxed_seqcst`  |
| Acquire | Relaxed | `_acq_failrelaxed`       | `_acquire_relaxed` |
| Acquire | Acquire | `_acq`                   | `_acquire_acquire` |
| Acquire | SeqCst  | :x:                      | `_acquire_seqcst`  |
| Release | Relaxed | `_rel`                   | `_release_relaxed` |
| Release | Acquire | :x:                      | `_release_acquire` |
| Release | SeqCst  | :x:                      | `_release_seqcst`  |
| AcqRel  | Relaxed | `_acqrel_failrelaxed`    | `_acqrel_relaxed`  |
| AcqRel  | Acquire | `_acqrel`                | `_acqrel_acquire`  |
| AcqRel  | SeqCst  | :x:                      | `_acqrel_seqcst`   |
| SeqCst  | Relaxed | `_failrelaxed`           | `_seqcst_relaxed`  |
| SeqCst  | Acquire | `_failacq`               | `_seqcst_acquire`  |
| SeqCst  | SeqCst  | (none)                   | `_seqcst_seqcst`   |

0 files changed, 0 insertions, 0 deletions