feat: unquoted escaping added

[sirkon]

I have a case where I construct keys with concatenation. Need to concatenate in a standalone buffer with the current API, meaning excessive copying. The proposed "unquoted" API solves this issue.

• I moved actual formatting logic from format_string to format_raw
• I decided to put #[inline(always)] on format_string and format_unquoted. My first intention was to keep public inline semantics and put that #[inline(always)] on format_raw functions, but there're issues with inlining and target_feature. Anyway, both format_string and format_unquoted are tiny now, so this should not change much compared to what it have been.

[codspeed-hq]

Merging this PR will not alter performance

✅ 3 untouched benchmarks

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_{Comparing sirkon:main (4ce101b) with main (6f12669)}