Rollup merge of #47193 - cramertj:result-opts, r=TimNN

Add transpose conversions for nested Option and Result

These impls are useful when working with combinator
methods that expect an option or a result, but you
have a `Result<Option<T>, E>` instead of an `Option<Result<T, E>>`
or vice versa.

diff --cc src/libcore/option.rs
Simple merge