Pre-RFC: Deprecation and separation of the dead_code lint

its an extremely useful way to silence all dead code warnings.

Its not though. It doesn't cover things like imports, macros, and assignments. Unused would be the correct lint here and the current name of dead_code and unused does a terrible job of communicating this. Adding an unused_items lint that covers all items, (the incorrectly stated affect of dead_code) would work better for this purpose.