Revert "Rollup merge of #136355 - GuillaumeGomez:proc-macro_add_value_retrieval_methods, r=Amanieu"

This reverts commit 08dfbf49e3, reversing
changes made to 10bcdad7df.

compiler/rustc_ast/src/util/literal.rs

@@ -2,7 +2,7 @@
 
 use std::{ascii, fmt, str};
 
-use literal_escaper::{
+use rustc_lexer::unescape::{
     MixedUnit, Mode, byte_from_char, unescape_byte, unescape_char, unescape_mixed, unescape_unicode,
 };
 use rustc_span::{Span, Symbol, kw, sym};