fix(ext/node): use primordials in ext/node/polyfills/internal/normalize_encoding.mjs (denoland#29283)

Towards denoland#24236. Replaces the `.toLowerCase` method with its equivalent
primordial method.

Author: jbronder

ext/node/polyfills/internal/normalize_encoding.mjs

@@ -1,7 +1,7 @@
 // Copyright 2018-2025 the Deno authors. MIT license.
 
-// TODO(petamoriken): enable prefer-primordials for node polyfills
-// deno-lint-ignore-file prefer-primordials
+import { primordials } from "ext:core/mod.js";
+const { StringPrototypeToLowerCase } = primordials;
 
 export function normalizeEncoding(enc) {
   if (enc == null || enc === "utf8" || enc === "utf-8") return "utf8";
@@ -13,14 +13,14 @@ export function slowCases(enc) {
     case 4:
       if (enc === "UTF8") return "utf8";
       if (enc === "ucs2" || enc === "UCS2") return "utf16le";
-      enc = `${enc}`.toLowerCase();
+      enc = StringPrototypeToLowerCase(`${enc}`);
       if (enc === "utf8") return "utf8";
       if (enc === "ucs2") return "utf16le";
       break;
     case 3:
       if (
         enc === "hex" || enc === "HEX" ||
-        `${enc}`.toLowerCase() === "hex"
+        StringPrototypeToLowerCase(`${enc}`) === "hex"
       ) {
         return "hex";
       }
@@ -31,7 +31,7 @@ export function slowCases(enc) {
       if (enc === "UTF-8") return "utf8";
       if (enc === "ASCII") return "ascii";
       if (enc === "UCS-2") return "utf16le";
-      enc = `${enc}`.toLowerCase();
+      enc = StringPrototypeToLowerCase(`${enc}`);
       if (enc === "utf-8") return "utf8";
       if (enc === "ascii") return "ascii";
       if (enc === "ucs-2") return "utf16le";
@@ -41,30 +41,30 @@ export function slowCases(enc) {
       if (enc === "latin1" || enc === "binary") return "latin1";
       if (enc === "BASE64") return "base64";
       if (enc === "LATIN1" || enc === "BINARY") return "latin1";
-      enc = `${enc}`.toLowerCase();
+      enc = StringPrototypeToLowerCase(`${enc}`);
       if (enc === "base64") return "base64";
       if (enc === "latin1" || enc === "binary") return "latin1";
       break;
     case 7:
       if (
         enc === "utf16le" || enc === "UTF16LE" ||
-        `${enc}`.toLowerCase() === "utf16le"
+        StringPrototypeToLowerCase(`${enc}`) === "utf16le"
       ) {
         return "utf16le";
       }
       break;
     case 8:
       if (
         enc === "utf-16le" || enc === "UTF-16LE" ||
-        `${enc}`.toLowerCase() === "utf-16le"
+        StringPrototypeToLowerCase(`${enc}`) === "utf-16le"
       ) {
         return "utf16le";
       }
       break;
     case 9:
       if (
         enc === "base64url" || enc === "BASE64URL" ||
-        `${enc}`.toLowerCase() === "base64url"
+        StringPrototypeToLowerCase(`${enc}`) === "base64url"
       ) {
         return "base64url";
       }