Rollup merge of #138084 - nnethercote:workspace-lints, r=jieyouxu

Use workspace lints for crates in `compiler/`

This is nicer and hopefully less error prone than specifying lints via bootstrap.

r? ``@jieyouxu``

compiler/rustc_index/Cargo.toml

@@ -21,3 +21,6 @@ nightly = [
 ]
 rustc_randomized_layouts = []
 # tidy-alphabetical-end
+
+[lints]
+workspace = true

compiler/rustc_index/src/lib.rs

@@ -4,7 +4,6 @@
 #![cfg_attr(feature = "nightly", feature(extend_one, step_trait, test))]
 #![cfg_attr(feature = "nightly", feature(new_range_api))]
 #![cfg_attr(feature = "nightly", feature(new_zeroed_alloc))]
-#![warn(unreachable_pub)]
 // tidy-alphabetical-end
 
 pub mod bit_set;