util: optimize toASCIILower function using V8s native toLowerCase

PR-URL: https://github.com/nodejs/node/pull/61107
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

lib/internal/mime.js

@@ -23,6 +23,8 @@ const END_BEGINNING_WHITESPACE = /[^\r\n\t ]|$/;
 const START_ENDING_WHITESPACE = /[\r\n\t ]*$/;
 
 function toASCIILower(str) {
+  // eslint-disable-next-line no-control-regex
+  if (!/[^\x00-\x7f]/.test(str)) return StringPrototypeToLowerCase(str);
   let result = '';
   for (let i = 0; i < str.length; i++) {
     const char = str[i];