Clean up rustc_*/Cargo.toml.

- 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.

compiler/rustc/Cargo.toml

@@ -4,16 +4,21 @@ version = "0.0.0"
 edition = "2021"
 
 [dependencies]
-rustc_driver = { path = "../rustc_driver" }
-rustc_driver_impl = { path = "../rustc_driver_impl" }
+# tidy-alphabetical-start
 
 # Make sure rustc_codegen_ssa ends up in the sysroot, because this
 # crate is intended to be used by codegen backends, which may not be in-tree.
 rustc_codegen_ssa = { path = "../rustc_codegen_ssa" }
+
+rustc_driver = { path = "../rustc_driver" }
+rustc_driver_impl = { path = "../rustc_driver_impl" }
+
 # Make sure rustc_smir ends up in the sysroot, because this
-# crate is intended to be used by stable MIR consumers, which are not in-tree
+# crate is intended to be used by stable MIR consumers, which are not in-tree.
 rustc_smir = { path = "../rustc_smir" }
+
 stable_mir = { path = "../stable_mir" }
+# tidy-alphabetical-end
 
 [dependencies.jemalloc-sys]
 version = "0.5.0"
@@ -21,7 +26,9 @@ optional = true
 features = ['unprefixed_malloc_on_supported_platforms']
 
 [features]
+# tidy-alphabetical-start
 jemalloc = ['jemalloc-sys']
 llvm = ['rustc_driver_impl/llvm']
 max_level_info = ['rustc_driver_impl/max_level_info']
 rustc_use_parallel_compiler = ['rustc_driver_impl/rustc_use_parallel_compiler']
+# tidy-alphabetical-end