Production lint category

[Kestrer]

About

This lint category collects all production code related lints, currently only including todo, unimplemented, dbg_macro, print_stdout and use_debug. This allows people to easily check whether they should release their code without having to remember the names of multiple lints and have to add and remove them, and allows Clippy to add more similar lints and have them be automatically enabled for all Rust production builds. Having these lints being in the restriction category doesn't really make sense because they are very useful for all Rust projects, just not all the time.

Drawbacks

It is a whole new lint category for just a couple lints.