suggest adding a where-clause when there is an unmet trait-bound that can be satisfied if some type can implement it.
to get the `Sized` error usable, since that hits new users frequently. Further work is needed for the error reporting for non-Sized cycle cases; those currently just fallback to the old path. Also adjust tests.
This commit is an implementation of [RFC 1236] and [RFC 1323] which rename the `thread::catch_panic` function to `panic::recover` while also replacing the `Send + 'static` bounds with a new `PanicSafe` bound. [RFC 1236]: https://github.com/rust-lang/rfcs/pull/1236 [RFC 1323]: https://github.com/rust-lang/rfcs/pull/1323 cc #27719