fs: use fs.writev() internally

Avoid using internal API in fs implementation.

PR-URL: #29189
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

lib/internal/fs/streams.js

@@ -2,10 +2,6 @@
 
 const { Math, Object } = primordials;
 
-const {
-  FSReqCallback,
-  writeBuffers
-} = internalBinding('fs');
 const {
   ERR_INVALID_ARG_TYPE,
   ERR_OUT_OF_RANGE
@@ -325,18 +321,6 @@ WriteStream.prototype._write = function(data, encoding, cb) {
 };
 
 
-function writev(fd, chunks, position, callback) {
-  function wrapper(err, written) {
-    // Retain a reference to chunks so that they can't be GC'ed too soon.
-    callback(err, written || 0, chunks);
-  }
-
-  const req = new FSReqCallback();
-  req.oncomplete = wrapper;
-  writeBuffers(fd, chunks, position, req);
-}
-
-
 WriteStream.prototype._writev = function(data, cb) {
   if (typeof this.fd !== 'number') {
     return this.once('open', function() {
@@ -356,7 +340,7 @@ WriteStream.prototype._writev = function(data, cb) {
     size += chunk.length;
   }
 
-  writev(this.fd, chunks, this.pos, function(er, bytes) {
+  fs.writev(this.fd, chunks, this.pos, function(er, bytes) {
     if (er) {
       self.destroy();
       return cb(er);