🐛 Crash at escaped extended ascii character within regex expression  #4689

Environment information

Cannot run rome rage, issue found by fuzzer.

**Additional Context**: 
Discovered by: Implement round-trip fuzzers for finding correctness bugs [#4559](https://github.com/rome/tools/pull/4559)

What happened?

An expression of the form: forward slash + backward slash + extended ascii character causes a crash with thread '<unnamed>' panicked at 'assertion failed: self.source.is_char_boundary(self.position)', /rome/tools/crates/rome_js_parser/src/lexer/mod.rs:545:9

Example failing cases (€ can be replaced with any extended ascii character):

1. /\€
2. /\€/

Not failing:

1. /\

Affected Formatters:
rome_format_d_ts
rome_format_jsx
rome_format_module
rome_format_script
rome_format_tsx
rome_format_typescript

Expected result

Should not crash.

Code of Conduct

• I agree to follow Rome's Code of Conduct