Remove last traces of identifier hygiene from HIR
e783a0a5e3
removed the [last](https://github.com/rust-lang/rust/pull/33654#discussion_r63415218) [use](https://github.com/rust-lang/rust/pull/33654#discussion_r63416284) of hygiene at post-resolve compilation stages, so we can avoid renaming during lowering to HIR and just keep original names.
r? @nrc