- Sort dependencies and features sections.
- Add `tidy` markers to the sorted sections so they stay sorted.
- Remove empty `[lib`] sections.
- Remove "See more keys..." comments.
Excluded files:
- rustc_codegen_{cranelift,gcc}, because they're external.
- rustc_lexer, because it has external use.
- stable_mir, because it has external use.
There's currently a deadlock with tracing when RUSTC_LOG is enabled.
Downgrade tracing-core for now to avoid blocking the other updates.
syns upgrades cause some nontrivial changes in the diagnostics derive tests,
which are best dealt with in another PR.
