48691ea6e6
Remove (lots of) dead code Builds on - [ ] https://github.com/rust-lang/rust/pull/83161 - [x] https://github.com/rust-lang/rust/pull/83230 - [x] https://github.com/rust-lang/rust/pull/83197. Found with https://github.com/est31/warnalyzer. See https://github.com/rust-lang/rust/pull/77739 for a similar change in the past. Dubious changes: - Maybe some of the dead code in rustc_data_structures should be kept, in case someone wants to use it in the future? TODO: - [ ] check if any of the comments on the deleted code should be kept. - [x] update the compiler documentation; right now it fails to build - [x] finish moving `cfg(test)` changes into https://github.com/rust-lang/rust/pull/83197 cc `@est31`