Allow passing server parameters on form submit

When you do something like this:

```php
$form = $crawler->selectButton('Submit')->form();
$crawler = $client->submit($form, [
'foo' => 'bar',
]);
```

You can't pass any server value. But it can be useful, for example, to passe XHR header: https://stackoverflow.com/a/9505494/1731473

Current possible workaround:

```php
$crawler = $client->request($form->getMethod(), $form->getUri(), $form->getPhpValues(), $form->getPhpFiles(), [
'HTTP_X-Requested-With' => 'XMLHttpRequest',
]);
```

Start by tracing the client submit API and comparing it with the request workaround shown in the issue, including getMethod(), getUri(), getPhpValues(), getPhpFiles(), and server parameters. Done means submit accepts server values such as HTTP_X-Requested-With and forwards them while preserving the existing form data behavior.

Written by the indexing model from the issue text.