Include tests from rust-lang/rust for Debug derive

[JelteF]

Our Debug derive is intended to be a strict superset of the one provided by std. Otherwise it's not safe for people to do use derive_more::Debug, because their resulting derives might change.

To make sure we actually adhere to this intention we should run the tests from the rust-lang/rust repo. This directory contains the tests for derive(Debug) afaict, but also for some other derives: https://github.com/rust-lang/rust/tree/master/tests/ui/derives We should copy the relevant ones from that directory and add use derive_more::Debug to the top and ensure that they still pass.

Related to #289

[JelteF]

I took a look at the std tests, and they seem very basic and very specific to the exact errors that std creates for derives. So I don't really see a reason to include them in our library. Our own Debug tests are much more comprehensive. So I'm closing this.