Rollup merge of #58273 - taiki-e:rename-dependency, r=matthewjasper

Rename rustc_errors dependency in rust 2018 crates

I think this is a better solution than `use rustc_errors as errors` in `lib.rs` and `use crate::errors` in modules.

Related: rust-lang/cargo#5653

cc #58099

r? @Centril

src/libsyntax_ext/format.rs

@@ -3,8 +3,8 @@ use Position::*;
 
 use fmt_macros as parse;
 
-use crate::errors::DiagnosticBuilder;
-use crate::errors::Applicability;
+use errors::DiagnosticBuilder;
+use errors::Applicability;
 
 use syntax::ast;
 use syntax::ext::base::{self, *};