refactor(oxc): ban index methods on std::str::Chars

[shulaoda]

closes #6071

I will gradually improve the remaining code until I understand the usage of the new method.

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[codspeed-hq]

CodSpeed Performance Report

Merging #6075 will not alter performance

_{Comparing shulaoda:refactor/chars-enumerate (b5dee29) with main (c5deb32)}

Summary

✅ 29 untouched benchmarks

[Boshen]

Thank you for working on this. We may need ast-grep in our CI to prevent this before the clippy rule gets released.

[Boshen]

It was already added to ast-grep example when I posted the problem. https://ast-grep.github.io/catalog/rust/#beware-of-char-offset-when-iterate-over-a-string

[shulaoda]

Thank you for working on this. We may need ast-grep in our CI to prevent this before the clippy rule gets released.

Let me research how to add it to CI.

[shulaoda]

@Boshen cc

It seems unnecessary to modify the following.

crates/oxc_codegen/src/lib.rs|318 col 63| unsafe { std::str::from_utf8_unchecked(self.code()) }.chars().nth_back(n)
crates/oxc_linter/src/partial_loader/astro.rs|75 col 49| if let Some('/') = self.source_text.chars().nth(js_start - 2) {
crates/oxc_linter/src/rules/eslint/no_useless_escape.rs|199 col 33| let escape_char = char_text.chars().nth(1).unwrap();
crates/oxc_linter/src/rules/eslint/no_useless_escape.rs|227 col 60| if let Some(prev_char) = ctx.source_text().chars().nth(span.end as usize) {
crates/oxc_linter/src/rules/eslint/no_useless_escape.rs|233 col 65| if let Some(prev_prev_char) = ctx.source_text().chars().nth(span.start as usize - 1)
crates/oxc_linter/src/rules/eslint/no_useless_escape.rs|290 col 28| if let Some(c) = s.chars().nth(1) {
crates/oxc_linter/src/rules/oxc/only_used_in_recursion.rs|239 col 19| let c = s.chars().nth(i).unwrap();
crates/oxc_linter/src/utils/react.rs|256 col 37| name.starts_with("use") && name.chars().nth(3).map_or(true, char::is_uppercase)
crates/oxc_linter/src/utils/react.rs|259 col 40| // name.starts_with("use") && name.chars().nth(3).is_some_and(char::is_uppercase)
crates/oxc_minifier/src/node_util/mod.rs|393 col 38| let radix: u32 = match s.chars().nth(1) {
crates/oxc_prettier/src/format/mod.rs|84 col 66| if let Some(c) = p.source_text[self.span.end as usize..].chars().nth(1) {
crates/oxc_sourcemap/src/sourcemap_visualizer.rs|144 col 46| if ch == '\r' && content.chars().nth(i + 1) == Some('\n') {