try_err: Consider Try impl for Poll when generating suggestions
There are two different implementation of `Try` trait for `Poll` type:
`Poll<Result<T, E>>` and `Poll<Option<Result<T, E>>>`. Take them into
account when generating suggestions.
For example, for `Err(e)?` suggest either `return Poll::Ready(Err(e))` or
`return Poll::Ready(Some(Err(e)))` as appropriate.
Fixes#5855
changelog: try_err: Consider Try impl for Poll when generating suggestions
3d7e3fdffd