Auto merge of #134243 - nnethercote:re-export-more-rustc_span, r=jieyouxu

Re-export more `rustc_span::symbol` things from `rustc_span`.

`rustc_span::symbol` defines some things that are re-exported from `rustc_span`, such as `Symbol` and `sym`. But it doesn't re-export some closely related things such as `Ident` and `kw`. So you can do `use rustc_span::{Symbol, sym}` but you have to do `use rustc_span::symbol::{Ident, kw}`, which is inconsistent for no good reason.

This commit re-exports `Ident`, `kw`, and `MacroRulesNormalizedIdent`, and changes many `rustc_span::symbol::` qualifiers to `rustc_span::`. This is a 300+ net line of code reduction, mostly because many files with two `use rustc_span` items can be reduced to one.

r? `@jieyouxu`

Author: bors

compiler/rustc_abi/src/extern_abi/mod.rs

@@ -1,8 +1,7 @@
 use std::fmt;
 
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
-use rustc_span::symbol::sym;
-use rustc_span::{Span, Symbol};
+use rustc_span::{Span, Symbol, sym};
 
 #[cfg(test)]
 mod tests;

compiler/rustc_ast/src/ast.rs

@@ -31,8 +31,7 @@ use rustc_data_structures::sync::Lrc;
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
 pub use rustc_span::AttrId;
 use rustc_span::source_map::{Spanned, respan};
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span};
+use rustc_span::{DUMMY_SP, ErrorGuaranteed, Ident, Span, Symbol, kw, sym};
 use thin_vec::{ThinVec, thin_vec};
 
 pub use crate::format::*;