icu: make process.binding('icu') internal

PR-URL: https://github.com/nodejs/node/pull/23234
Refs: https://github.com/nodejs/node/issues/22160
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>

lib/buffer.js

@@ -1078,7 +1078,7 @@ if (process.binding('config').hasIntl) {
   const {
     icuErrName,
     transcode: _transcode
-  } = process.binding('icu');
+  } = internalBinding('icu');
 
   // Transcodes the Buffer from one encoding to another, returning a new
   // Buffer instance.