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/source_map.rs

@@ -24,7 +24,7 @@ use std::fs;
 use std::io;
 use log::debug;
 
-use crate::errors::SourceMapper;
+use errors::SourceMapper;
 
 /// Returns the span itself if it doesn't come from a macro expansion,
 /// otherwise return the call site span up to the `enclosing_sp` by