Update Rustfmt to 1.0 #55965
Description
Tracking for the edition. Blocking issues on Rustfmt are at https://github.com/rust-lang-nursery/rustfmt/issues?q=is%3Aopen+is%3Aissue+milestone%3A%221.0+%28edition+rc1%29%22 though none of these will actually block, so I think I'll update on Monday and be done.