core: fix const ptr::swap_nonoverlapping when there are pointers at odd offsets

[RalfJung]

Ensure that the pointer gets swapped correctly even if it is not stored at an aligned offset. This rules out implementations that copy things in a usize loop -- so our implementation needs to be adjusted to avoid such a loop when running in const context.

Part of #133668

[rustbot]

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[rustbot]

Some changes occurred to the intrinsics. Make sure the CTFE / Miri interpreter
gets adapted for the changes, if necessary.

cc @rust-lang/miri, @rust-lang/wg-const-eval

[oli-obk]

r=me with output blessed

[RalfJung]

@bors r=oli-obk

[bors]

📌 Commit af1c8da has been approved by oli-obk

It is now in the queue for this repository.

[RalfJung]

Somehow this does not show up in the queue?
@bors retry

[RalfJung]

@bors r=oli-obk

[bors]

💡 This pull request was already approved, no need to approve it again.

• There's another pull request that is currently being tested, blocking this pull request: Rollup of 5 pull requests #134687

[bors]

📌 Commit af1c8da has been approved by oli-obk

It is now in the queue for this repository.

[RalfJung]

@bors rollup