lib: use primordials for navigator.userAgent

PR-URL: https://github.com/nodejs/node/pull/50467
Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com>
Reviewed-By: Vinícius Lourenço Claro Cardoso <contact@viniciusl.com.br>
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>

lib/internal/navigator.js

@@ -2,6 +2,8 @@
 
 const {
   ObjectDefineProperties,
+  StringPrototypeIndexOf,
+  StringPrototypeSlice,
   Symbol,
 } = primordials;
 
@@ -23,7 +25,7 @@ const nodeVersion = process.version;
 class Navigator {
   // Private properties are used to avoid brand validations.
   #availableParallelism;
-  #userAgent = `Node.js/${nodeVersion.slice(1, nodeVersion.indexOf('.'))}`;
+  #userAgent = `Node.js/${StringPrototypeSlice(nodeVersion, 1, StringPrototypeIndexOf(nodeVersion, '.'))}`;
 
   constructor() {
     if (arguments[0] === kInitialize) {