[9.x] Add paymentRequired helper to Http Client response

[tjardoo]

This PR adds the paymentRequired to the Http Client Response class. The 402 error page was just merged into the framework [9.x] Add 402 exception view #45682

Currently we have to use the following code to check if a response is 402 Payment Required.

$response = Http::get('https://laravel.com');

if ($response->status() === 402) {
    doSomething();
}

With this PR you can do the following, which is a bit cleaner.

$response = Http::get('https://laravel.com');

if ($response->paymentRequired()) {
    doSomething();
}

Thanks!

[taylorotwell]

Just checking the status is fine.