Rollup merge of rust-lang#103919 - nnethercote:unescaping-cleanups, r=matklad

Unescaping cleanups

Some code improvements, and some error message improvements.

Best reviewed one commit at a time.

r? ````@matklad````

Author: Dylan-DPC

crates/syntax/src/validation.rs

@@ -5,9 +5,7 @@
 mod block;
 
 use rowan::Direction;
-use rustc_lexer::unescape::{
-    self, unescape_byte, unescape_byte_literal, unescape_char, unescape_literal, Mode,
-};
+use rustc_lexer::unescape::{self, unescape_byte, unescape_char, unescape_literal, Mode};
 
 use crate::{
     algo,
@@ -143,7 +141,7 @@ fn validate_literal(literal: ast::Literal, acc: &mut Vec<SyntaxError>) {
         ast::LiteralKind::ByteString(s) => {
             if !s.is_raw() {
                 if let Some(without_quotes) = unquote(text, 2, '"') {
-                    unescape_byte_literal(without_quotes, Mode::ByteStr, &mut |range, char| {
+                    unescape_literal(without_quotes, Mode::ByteStr, &mut |range, char| {
                         if let Err(err) = char {
                             push_err(2, (range.start, err));
                         }