Suggest adding feature when a function / method / module defined behind such feature and it's not enabled

[upsuper]

When I was trying to migrate my crate to reqwest 0.10, there is a confusing compile error stating

error[E0599]: no method named json found for type reqwest::async_impl::request::RequestBuilder in the current scope

I had a brief look at the doc and could still find it. I eventually realized that it requires an additional feature json (as the doc correctly points out but overlooked by me).

I believe the compiler should have enough information about functions / method / module which are defined behind a feature, so it can probably step in and suggest such feature for this kind of errors so that people don't need to check code or even Cargo.toml of the crate to know what to do.

[estebank]

Fixed by #109005