docs improvement std::sync::{PoisonError, TryLockError}

[lorepozo]

Addresses the PoisonError and TryLockError parts of #29377.
Adds examples and links.

r? @steveklabnik

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @steveklabnik (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

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[frewsxcv]

this looks great, thanks!

@bors r+ rollup

[bors]

📌 Commit 99c0c52 has been approved by frewsxcv

[lorepozo]

Whoops, I force-pushed to my branch to work on other changes before this was merged in (so GitHub automatically closed this PR). I assume bors will still include the commit in the next rollup anyway? @frewsxcv

[arielb1]

@lucasem

I think you're still in the bors queue.

[bors]

☔ The latest upstream changes (presumably #44936) made this pull request unmergeable. Please resolve the merge conflicts.

[Mark-Simulacrum]

Merged in #44936.