Rollup merge of rust-lang#72047 - Julian-Wollersberger:literal_error_reporting_cleanup, r=petrochenkov

Literal error reporting cleanup

While doing some performance work, I noticed some code duplication in `librustc_parser/lexer/mod.rs`, so I cleaned it up.

This PR is probably best reviewed commit by commit.

I'm not sure what the API stability practices for `librustc_lexer` are. Four public methods in `unescape.rs` can be removed, but two are used by clippy, so I left them in for now.
I could open a PR for Rust-Analyzer when this one lands.

But how do I open a PR for clippy? (Git submodules are frustrating to work with)

Author: RalfJung

clippy_lints/src/write.rs

@@ -483,8 +483,8 @@ fn check_newlines(fmtstr: &StrLit) -> bool {
     };
 
     match fmtstr.style {
-        StrStyle::Cooked => unescape::unescape_str(contents, &mut cb),
-        StrStyle::Raw(_) => unescape::unescape_raw_str(contents, &mut cb),
+        StrStyle::Cooked => unescape::unescape_literal(contents, unescape::Mode::Str, &mut cb),
+        StrStyle::Raw(_) => unescape::unescape_literal(contents, unescape::Mode::RawStr, &mut cb),
     }
 
     should_lint