Rollup merge of #144872 - connortsui20:once-poison-docs, r=Amanieu

Document Poisoning in `LazyCell` and `LazyLock`

Currently, there is no documentation of poisoning behavior in either `LazyCell` or `LazyLock`, even though both of them can be observed as poisoned by users.

`LazyCell` [plagyround example](https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=9cf38b8dc56db100848f54085c2c697d)

`LazyLock` [playground example](https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=f1cd6f9fe16636e347ebb695a0ce30c0)

# Open Questions

- [x] Is it worth making the implementation of `LazyLock` more complicated to ensure that the the panic message is `"LazyLock instance has previously been poisoned"` instead of `"Once instance has previously been poisoned"`? See the `LazyLock` playground link above for more context.
- [x] Does it make sense to move `LazyLock` into the `poison` module? It is certainly a poison-able type, but at the same time it is slightly different from the 4 other types currently in the `poison` module in that it is unrecoverable. I think this is more of a libs-api question.

``@rustbot`` label +T-libs-api

Please let me know if these open questions deserve a separate issue / PR!

Author: samueltardieu