[11.x] Helper methods to dump responses of the Laravel HTTP client

[morrislaptop]

Similar to #36466 this PR adds methods to the Response object returned by the HTTP Client.

The method signatures follow the methods from the TestResponse class for consistency.

Http::get($url)->dump($key = null);
Http::get($url)->dd($key = null);
Http::get($url)->dumpHeaders();
Http::get($url)->ddHeaders();

[PPrinsloo]

Nice, literally needed it this morning!