test: add test for readStream.path when fd is specified

Refs: #40252 (review)

PR-URL: #40359
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

test/parallel/test-fs-read-stream-fd.js

@@ -35,6 +35,8 @@ fs.writeFileSync(file, input);
 const fd = fs.openSync(file, 'r');
 const stream = fs.createReadStream(null, { fd: fd, encoding: 'utf8' });
 
+assert.strictEqual(stream.path, undefined);
+
 stream.on('data', common.mustCallAtLeast((data) => {
   output += data;
 }));