[8.x] Helper methods to dump requests of the Laravel HTTP client

[cerbero90]

Sometimes developers may need to inspect requests sent via the Laravel HTTP client. This PR aims to introduce the popular dump() and dd() helpers in the client so that this syntax is possible:

Http::dump()->get($url);
Http::dd()->post($url);

The helpers will dump both the instance of Illuminate\Http\Client\Request and the client options used to perform the request:

Illuminate\Http\Client\Request {#685 ▼
  #request: GuzzleHttp\Psr7\Request {#480 ▶}
  #data: []
}

array:10 [▼
  "http_errors" => false
  "laravel_data" => []
  "on_stats" => Closure($transferStats) {#504 ▶}
  "synchronous" => true
  "handler" => GuzzleHttp\HandlerStack {#724 ▶}
  "cookies" => GuzzleHttp\Cookie\CookieJar {#853 ▶}
  "allow_redirects" => array:5 [▶]
  "decode_content" => true
  "verify" => true
  "idn_conversion" => false
]

To keep the same behavior of the homonym methods in Collections, it is also possible to pass extra variables to dump:

Http::dump($var1, $var2)->get($url);
Http::dd($var3)->post($url);